feat(coach): follow-up chips under the latest answer

Up to three chips, derived on the server from what the turn read: the
other view of a table with a chart, the period before, a year earlier,
a wider window, and a metric a discovered pattern links to. A chip is
offered only when its read was done this turn and the record holds the
metric; the year-ago and wider-window chips also need the record's
first reading to reach back that far. The model may name chips in a
FOLLOWUPS block, but only to reorder ones the rules already allow; every
label is rendered from the catalog.

A tapped chip resolves against the chips stored on the conversation's
latest reply. "As a chart" and "as a table" are answered from the
stored table without a model call or a budget reservation: the rows are
copied unchanged and the message is tagged providerType "reuse". Other
chips run a normal turn with a server-written context line. A chip that
is no longer current falls back to a plain message.

A setting turns the chips off (absent means on).

docs/api/openapi.yaml

@@ -24988,6 +24988,10 @@ components:
                 - type: string
                   maxLength: 40
                 - type: "null"
+        followUpChips:
+          description: v1.39.4 — offer up to three follow-up chips under the Coach's latest answer. Absent means on; only `false`
+            switches them off.
+          type: boolean
         baseUpdatedAt:
           description: "Optimistic-concurrency base token: the `updatedAt` the client last read for this resource. Omit it for the
             legacy unconditional write (older clients are unaffected). When present, the write is guarded on the stored
@@ -46837,6 +46841,10 @@ components:
             - dismissedCadences
             - lastSuggestedAt
           additionalProperties: false
+        followUpChips:
+          description: v1.39.4 — offer up to three follow-up chips under the Coach's latest answer. Absent means on; only `false`
+            switches them off.
+          type: boolean
         updatedAt:
           description: "Optimistic-concurrency token: the stored row's `updatedAt` at read/write time. Echo it back as
             `baseUpdatedAt` on the next write. Opaque — only ever echo a server-returned value, never parse or
@@ -75367,6 +75375,10 @@ components:
             - dismissedCadences
             - lastSuggestedAt
           additionalProperties: false
+        followUpChips:
+          description: v1.39.4 — offer up to three follow-up chips under the Coach's latest answer. Absent means on; only `false`
+            switches them off.
+          type: boolean
       required:
         - tone
         - verbosity