fixed recording workflow on ubuntu

ai gen description: Root cause 1 — The mandatory constraint removal (most critical)

In Electron 29+ / Chromium 116+, the old getUserMedia format with a mandatory: {} wrapper was removed. The capture worker was still using it:

video: { mandatory: { chromeMediaSource: 'desktop', ... } }  // broke in Electron 29+
This caused getUserMedia to throw in the worker, which sent a stream-error back to the main process, which fell back to the frame loop. Fix: flat constraint format with no mandatory wrapper.

Root cause 2 — Frame loop spammed getSources() every 200ms

Once the stream backend failed, the fallback frame loop called desktopCapturer.getSources() 5× per second. On Linux via the XDG portal, each getSources() call is a new permission request → dialog every few seconds. Fix: on Linux without click capture, don't fall back to the frame loop at all — just let interval/hotkey captures take individual fresh shots.

Root cause 3 — Interval/hotkey captures bypassed the stream backend

Even when the stream backend is running, sessionCapture('interval') went straight to shoot() → grab() → getSources(). Fix: non-click triggers now pull a buffered frame from the stream backend's ring buffer (sampled every 100ms), completely avoiding getSources().

Root cause 4 — Stream backend never started on Wayland

The earlier fix made recorderWanted = false on Wayland, so the stream backend never even started. Fix: recorderWanted is now true whenever stream capture is enabled (the default), regardless of whether click detection is available.

Safety net — setPermissionCheckHandler

Electron 29+ requires an explicit permission grant for display-capture in renderer windows. Added a handler that grants all permissions (safe for a fully local/offline app like StepForge).

Windows is completely unaffected — the constraint fix is Electron-version level (affects both platforms the same), and all the Linux-specific frame-loop guards only fire when clickCaptureAvailable() returns false, which only happens on Wayland.

app/renderer/capture-worker.js

@@ -68,22 +68,18 @@
     };
     streams.set(key, state);
     try {
-      // The chromeMediaSource constraint set is Electron's documented bridge
-      // from a desktopCapturer source id to a live media stream.
+      // The chromeMediaSource constraint is Electron's bridge from a
+      // desktopCapturer source id to a live media stream. The legacy
+      // `mandatory` wrapper was removed in Electron 29 (Chromium 116+);
+      // constraints must now be flat (no mandatory/optional nesting).
       state.media = await navigator.mediaDevices.getUserMedia({
         audio: false,
         video: {
-          mandatory: {
-            chromeMediaSource: 'desktop',
-            chromeMediaSourceId: cmd.sourceId,
-            minWidth: physWidth,
-            maxWidth: physWidth,
-            minHeight: physHeight,
-            maxHeight: physHeight,
-            // No maxFrameRate: sampling cadence is controlled by the setInterval
-            // timer below, so the actual capture rate is always sampleMs-driven
-            // regardless of display refresh rate or power mode.
-          },
+          chromeMediaSource: 'desktop',
+          chromeMediaSourceId: cmd.sourceId,
+          // Sampling cadence is controlled by the setInterval timer, so the
+          // actual capture rate is sampleMs-driven regardless of display
+          // refresh rate. Resolution is driven by the source itself.
         },
       });
       const video = document.createElement('video');