feat: Harden CodexAcpAgent session state and permission handling

[charlesvien]

Changes

1. Initialize sessionState and codexConnection eagerly in the constructor instead of using ! assertions
2. Pass permissionMode, taskRunId and taskId from meta into createSessionState for all session creation paths (load, new, fork)
3. Fix double-counting of token usage by relying on sessionUpdate notifications instead of also adding response.usage
4. Remove redundant cancel() override, use inherited interrupt() and base class cancellation state
5. Use POSTHOG_NOTIFICATIONS.USAGE_UPDATE constant instead of hardcoded string
6. Escape newlines in system instructions passed to codex CLI args
7. Abort the session's AbortController on closeSession for proper async cleanup

How did you test this?

Manually

[charlesvien]

• feat: Harden CodexAcpAgent session state and permission handling #1487 👈 (View in Graphite)
• feat: give codex permissions support #1483
• feat: give codex system prompt via personality #1482
• feat: clean up session reloadin #1481
• feat: update codex adapter and migrate to base acp prxy for agent #1480
• feat: codex 5.4 default and pass to model #1479
• main

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[k11kirky]

Merge activity

• Apr 6, 9:47 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 6, 10:24 PM UTC: Graphite rebased this pull request as part of a merge.
• Apr 6, 10:33 PM UTC: @k11kirky merged this pull request with Graphite.