Adds a new "Export diagnostics" entry under the About section that bundles
daemon/web/desktop logs, machine info, and recent macOS crash reports into
a zip the user can share when reporting issues.
- Browser hits a new daemon HTTP endpoint and triggers a download.
- Electron uses an IPC bridge with the native save dialog and reveals the
saved file in Finder/Explorer; the Help menu also exposes it as a
fallback when the daemon is unresponsive.
Packaging + redaction lives in a new @open-design/diagnostics package so
both surfaces share it. Sensitive JSON keys, URL query secrets, and the
current user's home path are redacted before packaging.