[bobleer]

Summary

Fix several state races in the flow chat that show up mostly on peer device surfaces.

• Stale DialogTurnStarted. A delayed start event could reactivate a completed/cancelled/errored turn or supersede a newer admitted turn. It is now dropped.
• Cancellation ownership. USER_CANCEL awaited imports before resolving the target, so it could send the cancel to a newly selected device, and a failed old cancel moved a newer turn back to processing. Cancellation now captures its surface and turn, checks a cancellation generation, and never rolls back on behalf of an older request. LocalSessionDriver.cancel ignores a late outcome for another turn.
• Pending queue. remove/setStatus acted on the currently active surface, so a send settling after a device switch mutated the wrong queue. Peer queues were gated by local Runtime attach fences and never drained; the cancel gate was never released by an authoritative terminal record; two drains could overlap. Queue ops are now surface-scoped, peer queues drain once canonical history is ready, and an uncertain submission after a surface switch is kept as a failed draft instead of being dropped or resubmitted.
• History catalog revisions. A catalog revision change kept old loadedRanges/activeRange, so late pages from the old revision were accepted, and a live tail turn past the persisted catalog returned not-found. Cached windows are invalidated on revision change, stale retries use the current generation, and the reader reacquires its range before extending it.
• Lost peer acknowledgements. A peer HostInvoke mutation whose reply was lost surfaced as a generic error and a peer delete that actually succeeded was reported as failed. Such failures now carry the existing outcome_unknown: code, and an uncertain peer deletion is settled by an authoritative metadata read.

Type and Areas

Type: bug fix

Areas: web UI (flow chat, peer device adapter)

Motivation / Impact

Users switching between devices or cancelling during peer sessions could see revived turns, wrong-device cancels, stuck or duplicated queued messages, broken history scrolling after a catalog refresh, and false "delete failed" errors.

Verification

• npx vitest run src/flow_chat/store/FlowChatStore.test.ts src/flow_chat/services/flow-chat-manager src/flow_chat/state-machine/SessionStateMachine.test.ts src/flow_chat/components/modern/ModernFlowChatContainer.history-restore.test.tsx src/infrastructure/api/adapters/peer-device-adapter.test.ts in src/web-ui: all new tests pass. 4 existing PendingQueueModule localStorage persistence tests fail identically on unmodified main in my environment, so they are unrelated to this change.
• tsc --noEmit in src/web-ui

Remote scenarios: Peer Device Mode paths covered by unit tests with mocked transports only.

Reviewer Notes

AI-assisted change, lightly tested as listed above.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.