feat(labs): refuse a biomarker unit change while readings are linked

Readers label every linked reading with the marker's unit, so changing
it relabelled stored numbers without converting them. PUT
/api/biomarkers/{id} now answers 422 biomarkers.unit.locked with
meta.readingCount when the unit differs and any reading (tombstoned
ones included) is linked. The marker editor says so under the unit
field.

docs/api/openapi.yaml

@@ -14369,8 +14369,11 @@ paths:
       tags:
         - Labs
       summary: Edit a biomarker
-      description: Partial edit; omitted fields are untouched, an explicit null clears `context` / `panel` / a bound. Audits
-        as `biomarker.update`.
+      description: "Partial edit; omitted fields are untouched, an explicit null clears `context` / `panel` / a bound. Audits
+        as `biomarker.update`. Since v1.40.0 a `unit` different from the stored one is refused with 422
+        `biomarkers.unit.locked` while any reading is linked to the marker (`meta.readingCount` carries how many):
+        readers label every linked reading with the marker's unit, so a change would relabel stored numbers without
+        converting them. Sending the current unit, or changing it on a marker with no readings, is accepted."
       parameters:
         - in: path
           name: id
@@ -31719,29 +31722,30 @@ components:
                 auth.reproof.failed, auth.reproof.required, auth.reproof.too_weak, auth.scope.insufficient,
                 auth.stepup.required, auth.token.expired, auth.token.invalid; backup — backup.foreign_reference,
                 backup.key.missing, backup.payload.undecryptable, backup.restore.active, backup.section.missing,
-                backup.upload.too_large; body-site — body-site.invalid; coach — coach.budget.exceeded,
-                coach.conversation.invalidTitle, coach.conversation.notFound, coach.fenced.attachmentConflict,
-                coach.fenced.attachmentLimit, coach.fenced.attachmentNotFound, coach.fenced.attachmentNotIndexed,
-                coach.fenced.attachmentRequired, coach.fenced.attachmentUnavailable, coach.fenced.invalid,
-                coach.request.invalid; coach-prefs — coach-prefs.body.invalid_json, coach-prefs.body.invalid_shape;
-                consent — consent.ai.required; cycle — cycle.bulk.invalid, cycle.bulk.too_large, cycle.calendar.invalid,
-                cycle.calendar.range, cycle.cycles.invalid, cycle.day-log.conflict, cycle.day-log.invalid,
-                cycle.disabled, cycle.period.invalid, cycle.symptom.custom.invalid, cycle.symptom.custom.limit;
-                cycle-prefs — cycle-prefs.body.invalid_json, cycle-prefs.invalid; disable-coach —
-                disable-coach.body.invalid_json; documents — documents.chat.conversationNotFound,
-                documents.chat.invalid, documents.inbound.alreadyConfirmed, documents.inbound.alreadyPartlyConfirmed,
-                documents.inbound.budgetExceeded, documents.inbound.decryptFailed, documents.inbound.encounterNotFound,
-                documents.inbound.episodeNotFound, documents.inbound.extractFailed, documents.inbound.factNotFound,
-                documents.inbound.factNotPending, documents.inbound.factTypeMismatch, documents.inbound.fileTooLarge,
-                documents.inbound.fileType, documents.inbound.invalidMetadata, documents.inbound.invalidQuery,
-                documents.inbound.invalidUpdate, documents.inbound.localOcrDisabled, documents.inbound.notFound,
-                documents.inbound.notIndexed, documents.inbound.pdfNeedsAnthropic,
-                documents.inbound.providerUnsupported, documents.inbound.quotaExceeded, documents.inbound.rateLimited,
-                documents.inbound.restoreDuplicate, documents.inbound.restoreGone, documents.inbound.sourceAliasLimit,
-                documents.inbound.uploadBusy, documents.inbound.uploadTimeout, documents.inbound.vaccinationNotFound,
-                documents.sources.authRefused, documents.sources.badResponse, documents.sources.browserOnly,
-                documents.sources.invalidAddress, documents.sources.linkTargetNotFound, documents.sources.notConnected,
-                documents.sources.notFound, documents.sources.organizationRequired, documents.sources.originNotAllowed,
+                backup.upload.too_large; biomarkers — biomarkers.unit.locked; body-site — body-site.invalid; coach —
+                coach.budget.exceeded, coach.conversation.invalidTitle, coach.conversation.notFound,
+                coach.fenced.attachmentConflict, coach.fenced.attachmentLimit, coach.fenced.attachmentNotFound,
+                coach.fenced.attachmentNotIndexed, coach.fenced.attachmentRequired, coach.fenced.attachmentUnavailable,
+                coach.fenced.invalid, coach.request.invalid; coach-prefs — coach-prefs.body.invalid_json,
+                coach-prefs.body.invalid_shape; consent — consent.ai.required; cycle — cycle.bulk.invalid,
+                cycle.bulk.too_large, cycle.calendar.invalid, cycle.calendar.range, cycle.cycles.invalid,
+                cycle.day-log.conflict, cycle.day-log.invalid, cycle.disabled, cycle.period.invalid,
+                cycle.symptom.custom.invalid, cycle.symptom.custom.limit; cycle-prefs — cycle-prefs.body.invalid_json,
+                cycle-prefs.invalid; disable-coach — disable-coach.body.invalid_json; documents —
+                documents.chat.conversationNotFound, documents.chat.invalid, documents.inbound.alreadyConfirmed,
+                documents.inbound.alreadyPartlyConfirmed, documents.inbound.budgetExceeded,
+                documents.inbound.decryptFailed, documents.inbound.encounterNotFound, documents.inbound.episodeNotFound,
+                documents.inbound.extractFailed, documents.inbound.factNotFound, documents.inbound.factNotPending,
+                documents.inbound.factTypeMismatch, documents.inbound.fileTooLarge, documents.inbound.fileType,
+                documents.inbound.invalidMetadata, documents.inbound.invalidQuery, documents.inbound.invalidUpdate,
+                documents.inbound.localOcrDisabled, documents.inbound.notFound, documents.inbound.notIndexed,
+                documents.inbound.pdfNeedsAnthropic, documents.inbound.providerUnsupported,
+                documents.inbound.quotaExceeded, documents.inbound.rateLimited, documents.inbound.restoreDuplicate,
+                documents.inbound.restoreGone, documents.inbound.sourceAliasLimit, documents.inbound.uploadBusy,
+                documents.inbound.uploadTimeout, documents.inbound.vaccinationNotFound, documents.sources.authRefused,
+                documents.sources.badResponse, documents.sources.browserOnly, documents.sources.invalidAddress,
+                documents.sources.linkTargetNotFound, documents.sources.notConnected, documents.sources.notFound,
+                documents.sources.organizationRequired, documents.sources.originNotAllowed,
                 documents.sources.permissionMissing, documents.sources.rateLimited, documents.sources.redirected,
                 documents.sources.tokenRequired, documents.sources.unavailable, documents.sources.unreachable,
                 documents.sources.versionTooOld; encounter — encounter.invalid, encounter.link.invalid,