fix(agent-status): keep agent-status-types under its line cap

main already sits exactly at the 300-line max-lines cap for this file, so the single
`acceptedStatusSeq` field this branch adds pushed it to 301 once main's observation
facet merged in.

Declared the field as a mixin beside the observation facet instead. Both are per-write
facets mixed into `AgentStatusEntry` rather than fields a reporter supplies, so they
belong together — and the capped file loses a line rather than gaining one, since it
already imports from that module. No lint suppression.

src/shared/agent-status-observation.ts

@@ -62,6 +62,17 @@ export type AgentStatusObservation = {
  *  body, so a hook or OSC writer cannot declare its own provenance. */
 export type WithAgentStatusObservation = { observation?: AgentStatusObservation }
 
+/** Renderer-local count of ACCEPTED status writes this pane's row has taken. Incremented only by
+ *  the store's accept branch, off the row it replaces, and carried through by every field-level
+ *  rewrite — so it answers "did the pane report again?", which `updatedAt` cannot, because the
+ *  accept rule admits equal timestamps. Lives on the row rather than in a side table so no
+ *  teardown path can reset it out from under a reader (STA-4612). Never sent over IPC or
+ *  persisted to last-status.json.
+ *
+ *  Declared here beside the observation facet because both are per-write facets mixed into
+ *  `AgentStatusEntry` rather than fields a reporter supplies. */
+export type WithAcceptedStatusSeq = { acceptedStatusSeq?: number }
+
 // ─── THE ORDERING RULE ──────────────────────────────────────────────────────
 // `(authorityId, incarnation, revision)` is a total order ONLY within one authorityId.
 // A different authorityId means "incomparable", not "older" — the id is regenerated per

src/shared/agent-status-types.ts

@@ -3,7 +3,7 @@
 // a narrow interrupt fallback synthesizes a final `done` when an agent misses its cancellation hook.
 
 import type { AgentProviderSessionMetadata } from './agent-session-resume'
-import type { WithAgentStatusObservation } from './agent-status-observation'
+import type { WithAcceptedStatusSeq, WithAgentStatusObservation } from './agent-status-observation'
 import {
   normalizeInteractivePromptField,
   normalizeOptionalField,
@@ -152,14 +152,8 @@ export type AgentStatusEntry = {
    *  the transition may have been missed while no receiver was up, so freshness gates
    *  treat the row as stale immediately. Cleared by any accepted live event. */
   restoredUnconfirmed?: boolean
-  /** Renderer-local count of ACCEPTED status writes this pane's row has taken. Incremented only by
-   *  the store's accept branch, off the row it replaces, and carried through by every field-level
-   *  rewrite — so it answers "did the pane report again?", which `updatedAt` cannot, because the
-   *  accept rule admits equal timestamps. Lives on the row rather than in a side table so no
-   *  teardown path can reset it out from under a reader (STA-4612). Never sent over IPC or
-   *  persisted to last-status.json. */
-  acceptedStatusSeq?: number
-} & WithAgentStatusObservation
+} & WithAgentStatusObservation &
+  WithAcceptedStatusSeq
 
 export type MigrationUnsupportedPtyEntry = {
   ptyId: string