docs(measurements): label EXTERNAL and update the guide and contract

The measurements list already badges any row whose source is not MANUAL and
already builds its source filter from the shared enum, so both pick the new
value up on their own. What it needs is a name: `EXTERNAL` reads as a leaked
enum constant, and it is the only new value a user is expected to operate,
since it is an option in the filter and a badge on every bridged row.

Both label catalogues gain an entry. They are keyed by the enum, so a new
source without a label is a type error and the coverage guard fails the
suite — which is exactly what happened here, and is the reason this carries
a settings label too even though EXTERNAL sits on no priority ladder and so
never renders there.

The settings card's scope note and the Home Assistant guide both claimed
readings arrive "as if you had entered them by hand", which is no longer
true. Both now say the rows are marked as coming from an external device and
are still yours to correct, and the guide spells out that the payload must
not name a source at all.

The changelog entries go under Unreleased as Changed: v1.38.1 shipped the
token, so these describe a change to something people already have. They say
what that means in practice — rows written before this keep the old label
and cannot be sorted out afterwards, a batch re-push can duplicate because
the dedup key now carries the source, and an automation sending an explicit
`source` field has to drop it.

src/lib/i18n/source-labels.ts

@@ -41,6 +41,10 @@ export const MEASUREMENT_SOURCE_SETTINGS_LABEL_KEYS: Record<
   MCP: "settings.sections.sources.sourceLabels.MCP",
   GOOGLE_HEALTH: "settings.sections.sources.sourceLabels.GOOGLE_HEALTH",
   STRAVA: "settings.sections.sources.sourceLabels.STRAVA",
+  // v1.38.x — readings pushed in under a `measurements:write` token.
+  // Never offered in the ladder (it is on no default priority list), but
+  // the map is keyed by the enum, so the entry is not optional.
+  EXTERNAL: "settings.sections.sources.sourceLabels.EXTERNAL",
 };
 
 /**
@@ -66,6 +70,7 @@ export const MEASUREMENT_SOURCE_LIST_LABEL_KEYS: Record<
   MCP: "measurements.sourceMcp",
   GOOGLE_HEALTH: "measurements.sourceGoogleHealth",
   STRAVA: "measurements.sourceStrava",
+  EXTERNAL: "measurements.sourceExternal",
 };
 
 /**

src/lib/openapi/routes/auth.ts

@@ -1559,7 +1559,7 @@ export const authPaths: NonNullable<ZodOpenApiObject["paths"]> = {
       summary: "Mint a measurement-ingest token",
       description:
         "Mints a Bearer scoped to exactly `measurements:write` and audits the mint. THE RESPONSE CARRIES THE RAW TOKEN — the only place it ever exists; it is stored as an HMAC and no path re-reveals it.\n\n" +
-        "**What it can do.** `POST /api/measurements` and `POST /api/measurements/batch`, on its owner's own record, attributing `source: MANUAL`. An entry naming `APPLE_HEALTH` is refused 422 rather than relabelled: that source is half a dedup key the phone also writes into, it participates in the cross-source merge, and it is what decides the Apple Health card may claim a sync happened. For the same reason a write through this credential does not move the native client's sync checkpoint.\n\n" +
+        "**What it can do.** `POST /api/measurements` and `POST /api/measurements/batch`, on its owner's own record. Rows it writes carry `source: EXTERNAL`, resolved from the credential rather than taken from the body, so a reading pushed by a bridge stays distinguishable from one typed in by hand and can be picked out with the source filter. A body naming ANY source is refused 422 rather than relabelled — honouring it would defeat the label, overriding it silently would hand the caller rows it did not ask for. `APPLE_HEALTH` is the one that would do real damage: it is half a dedup key the phone also writes into, it participates in the cross-source merge, and it is what decides the Apple Health card may claim a sync happened. For the same reason a write through this credential does not move the native client's sync checkpoint. The rows stay editable by their owner, unlike a connected provider's — the hardware behind the token is the user's own.\n\n" +
         "**What it cannot do.** Everything else, including the measurement reads on the same paths, the edit and delete legs, and the export — a scope grants what it names and nothing adjacent. It cannot be pointed at a shared record: a request carrying the account selector is refused 403 before any grant is read, whatever grants its holder actually has. And it cannot mint another token, this endpoint included.\n\n" +
         "Minting requires a COOKIE SESSION. No Bearer credential reaches this endpoint at any scope, wildcard included — not because a wildcard lacks the reach, but because of the lifetimes involved: a native access token lives a day and what it could mint here lives a year, so admitting one would let a short-lived compromise leave behind a credential that outlives revoking it. Gated by the operator's instance-wide API switch. Body capped at 16 KiB; 10 mints per user per minute, and at most 10 live tokens held at once. Tokens appear in `GET /api/tokens` and are revoked at `DELETE /api/tokens/{id}` like any other — revoking frees a slot against the ceiling.",
       requestBody: {

src/lib/openapi/routes/measurements.ts

@@ -850,7 +850,7 @@ export const measurementPaths: NonNullable<ZodOpenApiObject["paths"]> = {
       summary: "Create one measurement (or a small array)",
       description:
         "Single ingest. The body may also be a bare ARRAY of the same objects — the mode the iOS client uses for a combined blood-pressure + pulse or dual-value glucose write — in which case `data` is the array of created rows in request order. Use `/api/measurements/batch` for Apple Health upload streams.\n\n" +
-        "Also reachable with a narrow `measurements:write` Bearer, which is the supported way to push readings from a scale, a watch bridge or a home-automation rule. That credential is confined to its owner's own record — a request carrying the account selector is refused 403 before any sharing grant is read, however the record is actually shared — and to `MANUAL` attribution, so an explicit `APPLE_HEALTH` source is refused 422 (`measurement.create.source_not_permitted`). The GET on this same path, and the PUT and DELETE beside it, name no scope and so refuse it.",
+        "Also reachable with a narrow `measurements:write` Bearer, which is the supported way to push readings from a scale, a watch bridge or a home-automation rule. That credential is confined to its owner's own record — a request carrying the account selector is refused 403 before any sharing grant is read, however the record is actually shared — and it may not attribute a source at all: rows it writes carry `source: EXTERNAL`, resolved from the credential, so a bridged reading stays distinguishable from a hand-typed one. A body naming ANY source, `MANUAL` included, is refused 422 (`measurement.create.source_not_permitted`). The GET on this same path, and the PUT and DELETE beside it, name no scope and so refuse it — though the rows themselves stay editable by their owner, unlike a connected provider's.",
       parameters: [idempotencyKeyParameter],
       requestBody: {
         required: true,
@@ -889,7 +889,7 @@ export const measurementPaths: NonNullable<ZodOpenApiObject["paths"]> = {
         ...recordWriteRateLimitResponse,
         "422": {
           description:
-            "Validation failed, or (`measurement.create.source_not_permitted`) a narrow `measurements:write` credential named `APPLE_HEALTH` as the source. Refused rather than relabelled, so the caller can fix the payload instead of discovering rows it did not ask for.",
+            "Validation failed, or (`measurement.create.source_not_permitted`) a narrow `measurements:write` credential named a source — any source. Refused rather than relabelled, so the caller can fix the payload instead of discovering rows it did not ask for.",
           content: { "application/json": { schema: errorEnvelope } },
         },
       },
@@ -991,7 +991,7 @@ export const measurementPaths: NonNullable<ZodOpenApiObject["paths"]> = {
       summary: "Apple Health batch ingest",
       description:
         "Up to 500 HealthKit entries per call. Idempotent via the `Idempotency-Key` header (replay window 24h). Per-entry status lets the iOS client advance its sync cursor accurately. v1.4.25 W8c adds an optional `deviceType` per entry — feed it from `HKDevice.model` so the cross-source canonical picker can break Apple-Watch-vs-iPhone ties; null/absent stays backward-compatible with v1.4.23 clients.\n\n" +
-        "Also reachable with a narrow `measurements:write` Bearer, for a bridge that is not the phone. Such a credential writes only on its owner's own record; its entries are attributed `MANUAL` whatever they omit, an entry naming `APPLE_HEALTH` is refused 422 (`measurement.batch.source_not_permitted`), and the call does not advance the native sync checkpoint — `lastSyncedAt` means the CLIENT delivered what it was holding, and a third-party push is not that.",
+        "Also reachable with a narrow `measurements:write` Bearer, for a bridge that is not the phone. Such a credential writes only on its owner's own record; its entries are attributed `EXTERNAL` and it may not name a source itself, so an entry carrying one — `MANUAL` and `APPLE_HEALTH` alike — is refused 422 (`measurement.batch.source_not_permitted`). `EXTERNAL` also gives those writes their own `(userId, type, source, externalId)` namespace, so a bridge's ids can never collide with the phone's. The call does not advance the native sync checkpoint — `lastSyncedAt` means the CLIENT delivered what it was holding, and a third-party push is not that.",
       requestBody: {
         required: true,
         content: { "application/json": { schema: batchPayloadSchema } },
@@ -1011,7 +1011,7 @@ export const measurementPaths: NonNullable<ZodOpenApiObject["paths"]> = {
         ...stdResponses,
         "422": {
           description:
-            "The batch exceeded the 500-entry limit (`measurement.batch.too_large`), failed validation, or (`measurement.batch.source_not_permitted`) carried an entry naming `APPLE_HEALTH` under a narrow `measurements:write` credential. Nothing was written in any of the three cases.",
+            "The batch exceeded the 500-entry limit (`measurement.batch.too_large`), failed validation, or (`measurement.batch.source_not_permitted`) carried an entry naming a source — any source — under a narrow `measurements:write` credential. Nothing was written in any of the three cases.",
           content: { "application/json": { schema: errorEnvelope } },
         },
       },

src/lib/openapi/routes/shared.ts

@@ -144,7 +144,7 @@ export const measurementTypeEnum = measurementTypeEnumBase.meta({
 export const measurementSourceEnum = measurementSourceEnumBase.meta({
   id: "MeasurementSource",
   description:
-    "Origin of the measurement. v1.4.23 added APPLE_HEALTH for the iOS HealthKit batch ingest path.",
+    "Origin of the measurement. v1.4.23 added APPLE_HEALTH for the iOS HealthKit batch ingest path. v1.38.x added EXTERNAL for rows pushed in under a narrow `measurements:write` Bearer — a scale, a watch bridge, a home-automation rule. No client may name that value on a write; the server resolves it from the credential.",
 });
 
 export const loginPasswordSchema = loginPasswordSchemaBase.meta({