Make Codex status transcript-driven

[khoi]

Summary

• Problem: Codex tab activity still entered .running from managed tool hooks instead of the transcript lifecycle.
• Why it matters: startup and resume could miss already-active turns, and status could drift from the real Codex turn state.
• What changed: Codex running and idle state now come from transcript lifecycle events, startup reads the transcript snapshot before tailing, managed Codex hooks were reduced to SessionStart, UserPromptSubmit, and Stop, and the follow-up simplify pass removed duplicated turn-prep and activity-handling branches.
• What did NOT change (scope boundary): completion notifications still use Stop, running subtitle priority still comes from transcript content, and other agent integrations were not changed.

Rationale

The transcript is the only source that actually describes turn start, turn progress, and turn completion. Driving status from hook side effects left a blind spot on resume and kept Codex activity coupled to events that are not authoritative. This change moves status to the same source of truth that already drives running detail, while keeping hook handling limited to session setup and structured completion.

User-visible / Behavior Changes

• Codex tabs enter .running when transcript lifecycle events report a started turn, including startup and resume from an already-active transcript.
• Codex tabs return to .idle on transcript completion and abort events, with Stop still acting as the structured completion fallback.
• UserPromptSubmit no longer marks Codex running by itself.
• Stale Codex tool hook events no longer drive tab status.

Diagram (if applicable)

Before:
[Codex hook fires] -> [tab set running]
[startup/resume after started event] -> [monitor starts at EOF] -> [tab can stay idle]

After:
[SessionStart or UserPromptSubmit] -> [monitor arms from transcript snapshot]
[task_started / turn_started] -> [tab running]
[reasoning / tool / assistant message] -> [running detail updates]
[task_complete / turn_complete / turn_aborted] -> [tab idle]

Human Verification

• Verified scenarios: focused regression tests for hook settings, installer rewrite behavior, transcript startup snapshots, running-detail priority, ignored stale hook events, and transcript-driven running and idle transitions in the registry and session store.
• Edge cases checked: startup and resume with an already-active transcript, stale final snapshots before the next turn, UserPromptSubmit without forcing running, transcript abort/completion paths, and the simplification pass preserving the same registry/session-store behavior.
• What you did not verify: manual app interaction in a launched macOS build.
• How can a human manually verify this: install the Codex hooks, start a turn and confirm the tab only becomes running after transcript start events, resume into an already-running Codex session and confirm the tab is already running from the transcript snapshot, then complete or abort the turn and confirm the tab returns to idle while Stop still delivers completion notifications.