[vinayagg]

What broke
Teammates could not identify the same externally shared input/output folder when it appeared under different local paths, or verify that their file-sharing service was synchronizing it.

Why
The client had run-folder settings but no shared folder identity, per-client mapping, or external synchronization handshake.

What changed

• Add team and thread input/output identity markers, local mappings, and Files controls.
• Preserve old folders and markers when mappings change; report missing markers without recreating them at startup.
• Verify external synchronization in both directions without sending the challenge token through Bees peer transport.
• Exclude control files from new uploads and generated results while retaining compatibility with existing attachments.
• Prepare version 0.3.3 and its changelog, including the previously merged optional-runtime download changes.

Tested
npm run check passed with version 0.3.3, including 221 client tests, the remaining checks, and both UI builds. New coverage includes separate local paths, restart behavior, scheduled threads, folder identity validation, false-positive probes, access checks, cleanup, upload filtering, and generated-result filtering.

Not touched
This adds folder recognition and checks, not automatic external-folder import/delivery or WebRTC. Live Google Drive/SharePoint synchronization has not been tested.

Existing dependency alerts remain: ZIP in the Windows updater (including a critical advisory), GLib in the Linux UI stack, and development-only KaTeX. Windows updates in the current release feed use EXE installers, and downloaded updater packages are verified against the signing key and release version before installation. This PR does not remediate those inherited dependency advisories.