Check a rendered video

1. Use the project folder the user named, else the cwd (absolute path). It must have been rendered (render_submit); otherwise offer the render skill.
2. Call mcp__plugin_video-studio_engine__qa_run {project_dir} (add quality: "final" or "preview" to pick a render; default is the latest).
3. Report the status (pass, warn, fail) and each finding as id: detail, with its fix. Context:
   • With the silent voice (or voice.mode: none and no music), silence and loudness are reported as not measured, never as warnings.
   • frozen_frames fails when frozen time (still for 1 s or more) exceeds acceptance.max_frozen_pct of the runtime (default 15%). It is never "expected": a frozen reel reads as a slideshow. Fix the listed stretches with motion (a motion scene, camera moves, staged reveals) or cut them.
   • motion_density (big visual changes per second, from scene-change detection) and longest_static (longest stretch with no big change) fail only against the spec's acceptance.min_changes_per_sec and acceptance.max_static_sec; otherwise they are reported for context. Smooth continuous motion is not a "big change"; cuts, reveals and new states are. hold checks acceptance.hold_ms the same way.
   • moving (the share of frames where the picture moves at all, frame to frame) complements motion_density: a slow zoom, drift or crossfade counts as moving on every frame but is not a big change, while a hard cut is a big change but only one moving frame. A cut-only slideshow scores high changes/s and a low moving %; a slow Ken Burns the reverse. It fails only below acceptance.min_moving_pct. Fix: keep the holds alive (a slow camera move, easing elements, a crossfade). moving and frozen_frames can both be high: frozen means the whole frame barely changes, moving means anything changes (luma). High on both = only small parts move (a breathing glow, a blinking cursor) while the frame reads as still; give those stretches a bigger change.
   • loop_seam (with master.loop): the last frame must match the first (SSIM ≥ 0.99) and the audio level must not jump across the seam (under 6 dB).
   • flashing: fails above 3 flashes in any 1 s window (no acceptance override; flashes that fast can trigger seizures) and warns on single-frame luma spikes (a lone white or black frame mid-clip). It is measured on each frame's mean luma, an approximation of WCAG 2.3.1 general flashes: a flash in part of the frame counts less, and red flashes are not measured, so say so when the reel has strobing red. Fix: slow the flashing to 3/s or less, lower its contrast or shrink it; replace or fade a lone spike frame (qa/report.md lists the times).
   • av_sync: the audio must start within one frame of the video (fail) and last as long as the video's frames, within one frame plus 10 ms (warn). Not applicable without an audio track. Renders so far measured a 0 ms offset; on a failure, report the measured offset, re-render and, if it persists, run /video-studio:doctor (the ffmpeg build).
   • duration, resolution, aspect, black_frames or audio_stream failures mean the reel is not ready: suggest re-rendering (cached work is reused) and, if it persists, /video-studio:doctor.
4. The full report is in qa/report.md; dist/render-manifest.json now carries the new QA summary.