fix(windows): prefer managed node for whatsapp and desktop

[helix4u]

What does this PR do?

Fixes Windows Hermes-owned Node/npm resolution for WhatsApp setup/gateway and Desktop rebuild/update paths.

Windows installs place Hermes-managed portable Node directly under %LOCALAPPDATA%\hermes\node with node.exe and npm.cmd. Several Hermes subprocess paths still resolved bare node / npm from PATH, and the Desktop updater only prepended HERMES_HOME/node/bin, which is the POSIX layout. On Windows machines with a bad or elevation-triggering system Node/npm, WhatsApp setup/gateway and Desktop rebuilds could fail even though Hermes-managed Node was installed and working.

This adds one shared Python resolver for Hermes-managed Node/npm and uses it in the Python WhatsApp/Desktop/Web build paths, plus a matching Desktop main-process PATH helper for updater handoff/rebuild flows.

Related Issue

Support thread: https://discord.com/channels/1053877538025386074/1517614256680468600

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• hermes_constants.py: add Hermes-managed Node/npm lookup helpers for Windows %LOCALAPPDATA%\hermes\node, POSIX $HERMES_HOME/node/bin, and PATH augmentation.
• hermes_cli/main.py: use the managed Node/npm resolver for hermes whatsapp, web UI build, Electron redownload, Desktop build, and update-time Node dependency install.
• gateway/platforms/whatsapp.py: use managed Node/npm for WhatsApp requirement checks, bridge dependency install, bridge subprocess PATH, and bridge launch.
• apps/desktop/electron/main.cjs: prepend the Windows portable Node directory as well as the POSIX node/bin directory during updater handoff and in-app rebuild flows.
• tests/test_hermes_constants.py: add resolver coverage for Windows managed Node directory order, npm.cmd lookup, and PATH prepending.

How to Test

1. On Windows with Hermes installed under %LOCALAPPDATA%\hermes, make sure %LOCALAPPDATA%\hermes\node\node.exe and %LOCALAPPDATA%\hermes\node\npm.cmd exist.
2. Put a broken, incompatible, or elevation-triggering system Node/npm earlier on PATH, or remove system Node/npm from PATH.
3. Run hermes whatsapp and verify bridge dependency install/pairing uses Hermes-managed Node/npm instead of the bad PATH copy.
4. Start the gateway with WhatsApp enabled and verify the bridge launches instead of logging WhatsApp: Node.js not installed or bridge not configured.
5. Run the Desktop update/rebuild path and verify the Desktop build can find Hermes-managed npm from %LOCALAPPDATA%\hermes\node.

Scoped validation run in this checkout:

• python -m py_compile hermes_constants.py hermes_cli/main.py gateway/platforms/whatsapp.py tests/test_hermes_constants.py
• node --check apps/desktop/electron/main.cjs
• inline Python resolver assertions for Windows managed npm.cmd lookup and PATH prepending

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Screenshots / Logs

Reported support symptoms included:

• hermes whatsapp: npm install failed with no output.
• Later hermes whatsapp: WinError 740, elevation required.
• Gateway skipped WhatsApp with WhatsApp: Node.js not installed or bridge not configured and No adapter available for whatsapp.
• Manual %LOCALAPPDATA%\hermes\node\npm.cmd run pack succeeded where Desktop updater rebuild did not.

[kshitijk4poor]

Superseded by #49254, which salvages this work with your authorship preserved (your commit is cherry-picked verbatim at the base of that PR's stack) plus two follow-up commits on top:

• a sibling-coverage fix routing the hermes update desktop-rebuild gate through the same find_node_executable("npm") resolver (it was still on a bare shutil.which("npm")), and
• a small behavior-preserving refactor of the resolver helpers (hoist the command-name list out of the inner loop, drop a redundant os.environ.copy(), add reciprocal keep-in-sync comments between the Python and Electron path helpers).

Thanks for the fix, @helix4u — the cross-platform reasoning and the npm.cmd-before-npm.ps1 handling were spot on. Also filed #49259 to track consolidating the remaining hand-rolled managed-node resolution sites (mcp_tool, browser_tool, the TUI launcher, gateway service path) onto your new hermes_constants helpers as a separate follow-up.

Closing in favor of #49254.