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>

compiled/artplayer-plugin-multiple-subtitles.js

@@ -0,0 +1,7 @@
+/*!
+ * artplayer-plugin-multiple-subtitles.js v1.2.0
+ * Github: https://github.com/zhw2590582/ArtPlayer
+ * (c) 2017-2026 Harvey Zhao
+ * Released under the MIT License.
+ */
+!function(e,t){"object"===typeof exports&&"undefined"!==typeof module?module.exports=t():"function"==typeof define&&define.amd?(t.artplayerPluginMultipleSubtitles=t(),define(function(){return t.artplayerPluginMultipleSubtitles})):(e="undefined"!==typeof globalThis?globalThis:e||self).artplayerPluginMultipleSubtitles=t()}(this,function(){"use strict";var e={direction:"horizontal",snapToLines:!0,linePosition:"auto",lineAlign:"start",textPosition:"auto",positionAlign:"auto",size:100,alignment:"center"},t=function(t){t||(t={"&amp":"&","&lt":"<","&gt":">","&lrm":"\u200e","&rlm":"\u200f","&nbsp":"\xa0"}),this.entities=t,this.parse=function(a,s){a=a.replace(/\0/g,"\ufffd");var r=Date.now(),o=0,l=a.split(/\r\n|\r|\n/),f=!1,c=[],u=[],d=[];function p(e,t){d.push({message:e,line:o+1,col:t})}var m=l[o],g=m.length,h="WEBVTT",v=0,b=6;for("\ufeff"===m[0]&&(v=1,b+=1),(g<b||m.indexOf(h)!==0+v||g>b&&" "!==m[b]&&"\t"!==m[b])&&p('No valid signature. 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