fix: support Codex Desktop hosted by ChatGPT

[Haoo-7]

Summary

• Recognize Codex Desktop when its executable is hosted by ChatGPT.app.
• Discover project cwd and session metadata from Codex rollout transcripts when the shared app-server cwd is /.
• Ignore empty/root-cwd placeholder hooks that would overwrite a real discovered session.
• Parse Codex JSONL task_started, task_complete, turn_aborted, and turn_failed events into CodeIsland running/idle state.
• Treat Codex event messages as activity heartbeats so long turns are not reset to idle by the timeout watchdog.

Background

Codex has recently been integrated into ChatGPT as a multi-purpose host application. On macOS, the Codex executable can now run from:

/Applications/ChatGPT.app/Contents/Resources/codex

The shared app-server commonly reports / as its cwd, while the actual project cwd is stored in the rollout transcript metadata. Some desktop invocations also emit empty or root-cwd hook payloads.

The previous CodeIsland integration assumed the older standalone Codex.app layout and relied on hook/message parsing for live status, so sessions could be discovered but remained idle.

Test Plan

• swift build -c release --arch arm64 passes.
• Added JSONL parser coverage for Codex turn lifecycle events, latest turn recovery, and activity heartbeats.
• Added discovery coverage for ChatGPT.app executable paths, large session metadata, transcript cwd recovery, and placeholder hooks.
• swift test could not run on the development machine because the active Command Line Tools installation has no XCTest module; the test targets report this environment error. CI with a full Xcode toolchain should run the test suite.