feat: batch video upscaling with folder upload, directory save, and result comparison (#1051)

* feat: support batch video upscaling with folder upload and directory save

- Add multi-file selection and entire folder upload (webkitdirectory)
- Support drag & drop of both files and folders via FileSystemEntry API
- Add save directory picker using File System Access API (showDirectoryPicker)
- Process videos sequentially with per-file progress and status tracking
- Add right-side result list with click-to-compare functionality
- Add per-video duration and total batch duration display
- Add retry button for failed items with error detail display
- Remove auto-play on comparison viewer load
- Fix worker error handling: handle "error" command to reject stale promises
- Fix event listener accumulation in video comparison (AbortController)
- Fix XSS risk by escaping HTML in all innerHTML injections
- Fix URL revocation timing in download to prevent large file truncation
- Extract writeToSaveDirectory and truncateName helpers to reduce duplication
- Add Usage Guide panel explaining single/multiple/folder upload options

Files changed:
  docs/upscaler/index.html  (+1110/-181)
  docs/upscaler/upscaler.js (+110)

* fix: prevent auto-play and resource consumption during upscaling

- Set preload="metadata" on preview and comparison video elements
- Explicitly pause preview video after setting src in showVideoPreview
- Remove preview video seek sync from batch processing progress callbacks
  (was causing continuous decode during upscaling, wasting GPU resources)
- Remove preview video seek sync from retry progress callback
- All videos now require manual play; no background resource usage

* fix: improve upscaled video quality with higher bitrate and codec support

- Raise base bitrate from 2.5 Mbps (25e5) to 8 Mbps (8e6) for standard and
  firefox processors, preventing quality loss when source videos have high
  bitrates (e.g. 720p @ 16.7 Mbps was producing 1440p @ 10 Mbps, smaller
  than the original file)
- Double the bitrate for mediabunny processor (X.n1 * 2) to account for the
  4x pixel increase from 2x upscaling
- Add H.264 Level 5.1 (avc1.640033) and Level 5.2 (avc1.640034) codecs to
  the fallback lists, since Level 4.0 (avc1.640028, ~24.6 Mbps) cannot
  support the higher bitrates for 1440p+ outputs
- Add latencyMode: "quality" to VideoEncoder configs for both standard and
  firefox processors, prioritizing encoding quality over latency (suitable
  for offline processing)

* feat: add video data comparison panel for original vs upscaled metrics

- Add a comparison data table below the file info bar showing 6 metrics:
  Resolution, File Size, Duration, Est. Bitrate, Pixels, Process Time
- Display per-metric change percentage with color-coded indicators:
  green (↑) for improvements, red (↓) for regressions, gray for neutral
- Estimated bitrate calculated from file size × 8 / video duration
- Table renders after both original and upscaled video metadata loads
- Auto-hide panel on reset

* fix: make video data comparison panel full-width and responsive

- Move comparison data table from inside the left column to the full-width
  area below the left/right layout, so it is no longer constrained by the
  comparison viewer column width
- Remove table-fixed colgroup and overflow-x-auto that caused horizontal
  scrolling on smaller screens
- Table now uses w-full auto-layout, displaying all 4 columns (Metric,
  Original, Upscaled, Change) without requiring horizontal scrolling

---------

Co-authored-by: rionzhao <rionzhao@tencent.com>

docs/upscaler/worker/main.js

@@ -1764,7 +1764,7 @@ self.onmessage = async (event) => {
                 : { width: 2 * h.width, height: 2 * h.height };
             let y,
               U,
-              C = (b.width * b.height * 25e5) / 921600;
+              C = (b.width * b.height * 8e6) / 921600;
             const R = await E(r);
             if (t || a) {
               const e = a ? w : h;
@@ -1836,7 +1836,7 @@ self.onmessage = async (event) => {
               });
             const z = new B.fX(D);
             let I = b.width * b.height > 921600 ? "avc1.42003e" : "avc1.42001f",
-              O = ["avc1.640028", "avc1.64001e", "avc1.42003e", "avc1.42001f"];
+              O = ["avc1.640033", "avc1.640028", "avc1.64001e", "avc1.640034", "avc1.42003e", "avc1.42001f"];
             "firefox" === q && (O = ["avc1.42003e", "avc1.42001f"]);
             for (const e of O) {
               const t = {
@@ -1857,6 +1857,7 @@ self.onmessage = async (event) => {
                 height: b.height,
                 bitrate: Math.round(C),
                 framerate: 1e6 / F[0].duration,
+                latencyMode: "quality",
               },
               N = [],
               V = {},
@@ -2147,7 +2148,7 @@ self.onmessage = async (event) => {
                 : { width: 2 * d.width, height: 2 * d.height };
             let w,
               b,
-              y = (g.width * g.height * 25e5) / 921600;
+              y = (g.width * g.height * 8e6) / 921600;
             const k = await E(r);
             if (t || a) {
               const e = a ? v : d;
@@ -2207,8 +2208,10 @@ self.onmessage = async (event) => {
             const L = new B.fX(F);
             let M = g.width * g.height > 921600 ? "avc1.42003e" : "avc1.42001f";
             const G = [
+              "avc1.640033",
               "avc1.640028",
               "avc1.64001e",
+              "avc1.640034",
               "avc1.42003e",
               "avc1.42001f",
             ];
@@ -2231,6 +2234,7 @@ self.onmessage = async (event) => {
                 height: g.height,
                 bitrate: Math.round(y),
                 framerate: 1e6 / w.encoded_chunks[0].duration,
+                latencyMode: "quality",
               },
               D = [],
               z = new VideoDecoder({
@@ -2523,7 +2527,7 @@ self.onmessage = async (event) => {
           const B = new W.r({ format: new N.E1(), target: k }),
             E = new V.D0(f, {
               codec: "avc",
-              bitrate: X.n1,
+              bitrate: Math.round(X.n1 * 2),
               keyFrameInterval: 60,
             }),
             U = await w.getPrimaryVideoTrack();
@@ -2675,7 +2679,7 @@ self.onmessage = async (event) => {
             U = performance.now();
           console.log("Time to get WebSR: " + (U - g));
           const C = new W.r({ format: new N.E1(), target: E }),
-            P = new V.Dg({ codec: "avc", bitrate: X.n1, keyFrameInterval: 60 }),
+            P = new V.Dg({ codec: "avc", bitrate: Math.round(X.n1 * 2), keyFrameInterval: 60 }),
             R = await y.getPrimaryVideoTrack();
           if (!R && !R)
             return postMessage({