Linux port collaboration: phased re-land, attribution, and tester hardware

Context

@ForrestKnight, thank you for the six-phase work in ForrestKnight/videorc-linux. We are re-landing the Linux port phase by phase on current Videorc rather than merging the stale fork branches directly. L1 is now on main via #204, and the current phase contract is in docs/linux-port-plan.md.

Attribution and contribution contract

For every re-derived commit that materially uses the fork work, we propose preserving a Co-Authored-By trailer for you. Because Videorc is AGPL/open-core, we also need your DCO sign-off for contributed/re-landed work (Signed-off-by confirming you have the right to contribute it under the repository license). We can use an identity you confirm privately or your public GitHub noreply identity; no private address needs to be posted here.

Please confirm whether that attribution and DCO arrangement works for you.

Tester invitation

Would you also be willing to serve as the named Linux tester for L2 onward? The required box is real Ubuntu 24.04 x64 hardware with Wayland, PipeWire, a webcam, microphone, and /dev/dri access. CI or a VM can prove compile and AppImage packaging, but it cannot prove portal consent, camera/audio capture, VAAPI, lifecycle, or recording quality.

The next acceptance slices are:

1. LGPL-only encoder path: VAAPI with OpenH264 fallback, never libx264.
2. PipeWire microphone and sink-monitor desktop audio.
3. V4L2 camera capture and mask parity.
4. xdg-desktop-portal ScreenCast + PipeWire.
5. CPU composition and JPEG preview.
6. AppImage plus an isolated linux-alpha candidate/pilot/public lane.

If you can test, please share only the non-sensitive capability summary (Ubuntu version, GPU vendor, Wayland session, webcam/mic availability). Device IDs, logs, recordings, and local paths stay private.

Start with docs/linux-port-plan.md and the L1 work merged via #204, then review the six acceptance slices and the referenced videorc-linux fork. Done means the attribution and DCO arrangement is confirmed and a named tester verifies the required Ubuntu 24.04 hardware capabilities for later Linux phases.