#1297 land: plugin-reload-holds

Accepted agent delivery; branch-keyed search descriptor included.

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Summary by cubic

Changes plugin reload handling so tool calls already admitted to the AFT bridge are drained instead of aborted, without replaying mutations.

Behavior

• Release now waits up to 5 seconds for admitted calls; with a same-root replacement, calls keep their owner and return their real results beyond that deadline.
• Dispatched calls interrupted at owner shutdown reject with BridgeTransportUnknownOutcomeError; unsent calls reject with a typed not_sent refusal carrying LOCATION_RELOADED_NOT_SENT.
• Registration cleanup and consumer disposal are deferred until admitted calls settle, so late background tracking like bash_kill still works.