Fix Windows Electron launcher

[waml]

Summary

• Launch the bundled Electron package through its Node CLI instead of the Windows .cmd shim for the npm GUI path.
• Apply the same safer Electron launch resolution to MCP desktop auto-start.
• Add Windows CI coverage for npm install/test and the CLI help path.
• Normalize packed context display paths and make legacy path tests portable for Windows.
• Document Windows Chrome CDP setup and explicit browser executable configuration.

Validation

• node --check bin/agentify-desktop.mjs
• node --check mcp-lib.mjs
• node --check context-packer.mjs
• node bin/agentify-desktop.mjs --help
• npm test: 162/162 passing
• npm pack --dry-run --json: version 0.2.3, 40 files, no private/sprite workflow matches
• PR Fix Windows Electron launcher #51 proved the new Windows CI leg catches Windows-only failures; this PR is rebuilt cleanly from current main.