feat: connector update checking and one-click upgrade

[graydawnc]

Summary

• Check npm registry for newer connector versions on app launch (async, non-blocking) and cache results in main process
• Expose update availability in connector detail view with version diff display (v1.2.0 → v1.3.0)
• One-click "Update" button that downloads, installs, and reloads the connector in-place
• Manual "check for updates" available via IPC (re-checks all connectors on demand)
• Failed updates show inline error; old version continues working unaffected

Changes

Layer	File	What
Core	npm-install.ts	New checkForUpdates() — batch checks all installed connectors against npm registry using semver.gt
Main	index.ts	Startup update check (fire-and-forget), connector:check-updates and connector:update IPC handlers, extracted reloadConnectors() helper (deduped from 3 call sites)
Preload	index.ts	New checkUpdates() and update() methods on connectors API
Renderer	SettingsPanel.tsx	Update banner with version diff + Update button in connector detail view, per-connector error scoping

Design decisions

• No DB changes — version lives in package.json already
• No periodic polling — launch + manual check is sufficient
• No auto-update — user-initiated only
• No confirmation dialog — low-risk operation on already-trusted connector
• Bundled connectors excluded — managed by app updates

Test plan

• Install a connector, publish a newer version to npm, relaunch app → detail view shows update banner
• Click "Update" → connector updates, banner disappears, connector continues syncing
• Simulate network failure during update → error shown inline, old version unaffected
• Bundled connectors → no update banner shown
• Manual check via Settings → re-fetches latest versions

🤖 Generated with Claude Code