fix: detect Codex in nested ChatGPT macOS app bundle

[wsgxy986]

Summary

Fix Codex runtime discovery for newer ChatGPT macOS app bundles. First Tree 0.5.23 failed to start a Codex chat even though the executable was installed and runnable at:

/Applications/ChatGPT.app/Contents/Resources/codex-cli/CodexCLI.app/Contents/MacOS/codex

• Add the nested app bundle directory for both /Applications and ~/Applications.
• Preserve existing PATH precedence and legacy app locations.
• Add regression tests for system-wide and per-user installations.

Creating a ~/.local/bin/codex symlink and restarting the daemon restored discovery on the affected machine. This change makes that workaround unnecessary for this installation layout.

Validation

• Both new regression cases failed before the fix and passed afterward.
• All 35 tests in source-repos.test.ts and providers/codex/__tests__/binary.test.ts passed.
• Client TypeScript check passed.
• Repository-wide Biome check passed with existing warnings.
• git diff --check passed.
• Full repository typecheck and tests were attempted but blocked by the local dependency setup (ERR_PNPM_IGNORED_BUILDS). They are not claimed to have passed.

Notes

• No package version changes or public CLI changes.
• Related QA case: packages/qa/cases/runtime/daemon-probe-capability.md.
• Draft pending full CI validation and contributor identity/CLA checks.
• Replaces fix: detect Codex in nested ChatGPT macOS app bundle #2412 with a completed description; the code change is unchanged.

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