fix(desktop): extend PATH for dashboard backend so codex is discoverable on macOS

[liuhao1024]

Summary

macOS GUI apps launched via Launch Services (Finder/Dock) inherit a minimal PATH (/usr/bin:/bin:/usr/sbin:/sbin) that does not include ~/.hermes/node/bin. When the Electron desktop spawns the Python dashboard backend, this minimal PATH propagates to the child process, causing check_codex_binary() in agent/transports/codex_app_server.py to fail with:

Cannot enable codex_app_server runtime: codex CLI not found at 'codex'. Install with: npm i -g @openai/codex

Even though codex is already installed at ~/.hermes/node/bin/codex (Hermes's own bundled Node).

Fixes #41385

Root Cause

The self-update spawn path already extends PATH (line 1627 of main.cjs):

PATH: [path.join(HERMES_HOME, 'node', 'bin'), venvBin, process.env.PATH].filter(Boolean).join(path.delimiter)

But createPythonBackend() and createActiveBackend() — the two functions that build the dashboard backend descriptor — only set PYTHONPATH in their env object, leaving PATH at the inherited minimal value.

Fix

Add PATH extension to the env object in both createPythonBackend() and createActiveBackend(), prepending:

• ~/.hermes/node/bin (for codex and other Hermes-managed Node binaries)
• venv/bin (for the Python venv, when it exists)

This matches the existing pattern used by the self-update spawn and the per-profile backend spawn paths.

Test Plan

• Added regression test tests/test_desktop_dashboard_path.py verifying both functions include node/bin in PATH
• pytest tests/test_desktop_dashboard_path.py — 2/2 passed
• Manual: open Hermes desktop on macOS, run /codex-runtime on — should succeed

[teknium1]

Closing in favor of PR #44814, which just merged and supersedes this change — it includes the same ~/.hermes/node/bin + venv bin prepend for both createPythonBackend() and createActiveBackend() that you implemented here (you submitted that part first — thank you!), plus the POSIX sane-PATH completion for Homebrew bins and a tested shared helper (backend-env.cjs).

Your diagnosis of #41385 and the fix direction were correct and directly informed the final shape. Appreciate the contribution.