[codex] Add synced session message queue

[roackb2]

Summary

• persist queued prompts as core session state and drain them FIFO after active runs finish
• expose queue update/delete APIs and stream queue updates through control-plane session events
• let web-v2 and cli-v2 submit follow-up prompts while a run is active, with web edit/delete queue controls and a compact vertical queue panel
• document queue ownership and invariants in the session service README

Validation

• yarn typecheck
• yarn test
• yarn build

Note: yarn build still reports the existing Vite large chunk warning.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Drain queued prompts after every active run

When the active operation is /continue (sessionContinue calls continuePrompt) or compaction, this branch still accepts a new submit into queuedPrompts, but only submit runs install the onSettled handler that calls startNextQueuedPrompt. After a continue/compact run finishes there is no drain, so a prompt submitted during those operations remains persisted in the queue indefinitely until some later submit happens to kick it.

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