[codex] Start idle turns without reservations

[pakrym-oai]

Why

Goal continuation currently reserves an ActiveTurn without a running task while it revalidates persisted goal state. That creates a partial-active state just to schedule later work, and gives goals a separate turn-start flow from other idle work.

What changed

• Add try_start_turn_if_idle as the shared idle-only entry point, with task construction/spawning in start_turn and task execution in run_turn.
• Keep replace_turn preemptive for user turns, standalone shell commands, compaction, and review.
• Add turn_admission_lock so explicit replacement and idle-only startup cannot race during admission without using a taskless ActiveTurn reservation.
• Start goal continuation and queued pending work only when idle admission succeeds, removing goal-specific turn reservation and cleanup.
• Use new_default_turn() for automatic idle wake-ups so they follow one internal turn-id allocation path.
• Publish a real running task when idle startup wins, rather than reserving a taskless active turn before launch.

Behavior tradeoffs

• Goal continuation no longer claims an idle slot while checking that its goal is still current; explicit replacement retains priority when it competes with automatic idle work.
• Trigger-turn inter-agent wake-ups now use an internally allocated turn id instead of preserving the triggering submission id as the new turn id.
• Goal continuation and queued pending-work startup no longer use their prior pre-launch unknown-model warning call path.

Validation

• git diff --check
• Tests not run, per request to defer tests.

[pakrym-oai]

@codex review this

[chatgpt-codex-connector]

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Reviewed commit: 354aaeeccf

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[chatgpt-codex-connector]

Start foreground turns even after idle races

replace_turn is used for foreground requests such as user turns and shell commands, but it now delegates to the idle-only try_start_turn_if_idle. If the session is idle after abort_all_tasks and a pending-work or goal-continuation turn starts during the await in clear_connector_selection, this call just returns and the foreground input is neither queued nor run, so the user's request can disappear instead of replacing the background work. Foreground replacement should either win this race or retry/abort the turn that won it.

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[chatgpt-codex-connector]

Emit review entry before starting the review task

Because replace_turn now returns immediately after spawning the task, the ReviewTask can run to exit_review_mode before this function sends EnteredReviewMode below. In fast failure/cached review paths, clients and replay can observe ExitedReviewMode/TurnComplete before the review-entry marker, leaving the UI/history in the wrong order. Send the entry marker before starting the task, or make task startup wait until the marker is emitted.

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