fix(codex-discovery): discover macOS Codex installs

[huntharo]

Summary

PwrAgent Settings can now show macOS Codex installs even when the desktop app is launched with a sparse GUI PATH. Discovery checks current ChatGPT.app bundles, legacy Codex.app bundles, and fixed Homebrew install paths (/opt/homebrew/bin/codex, /usr/local/bin/codex) as known auto-candidates.

This fixes machines where /Applications/ChatGPT.app/Contents/Resources/codex exists but /Applications/Codex.app does not, and also machines where Codex is installed through Homebrew but /opt/homebrew/bin or /usr/local/bin is missing from the Electron launch environment. The Homebrew paths use the same Settings-visible application source as other known install locations, and the existing Homebrew preflight reader can report symlinked Cellar/Caskroom versions without executing when possible.

Normal executable discovery and version sorting still apply across discovered candidates. The returned discovery snapshot continues to expose parsed candidate versions through candidates[].version; callers can read the selected candidate's version, and resolveCodexCommand returns the selected command with its parsed version as well.

Verification

• pnpm --filter @pwrdrvr/codex-discovery test
• pnpm --filter @pwrdrvr/codex-discovery typecheck
• pnpm --filter @pwrdrvr/codex-discovery build
• Added regression coverage that the deterministic macOS candidate list includes both ChatGPT/Codex app bundles and Homebrew paths.
• Added regression coverage that parses a codex-cli 0.139.0. banner as 0.139.0 and exposes it on both the selected discovery candidate and resolveCodexCommand.
• Direct built-package probe with PATH=/usr/bin:/bin:/usr/sbin:/sbin and platform: "darwin" selected /opt/homebrew/bin/codex at 0.144.0, with /Applications/ChatGPT.app/Contents/Resources/codex at 0.144.0-alpha.4 also returned as a Settings-visible application candidate on this machine.

Note: this worktree did not have pnpm on shell PATH, so verification used the repo-pinned pnpm@10.33.0 via npm exec after installing dependencies. @pwrdrvr/agent-core was built first so workspace package exports resolved for the filtered checks.

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