feat: show optional SponsorBlock ranges on playback timeline

README.md

@@ -26,6 +26,7 @@ To run without installing, use `make run`. The built `.build/terebi.app` is self
 - **Stream queues:** integrations can supply an ordered yt-dlp/Miruro queue with `--new-instance --queue-file /absolute/queue.json`, or append without interrupting the running player using `--enqueue --queue-file /absolute/queue.json` (also for a single item). Enqueue starts playback if the player is empty or not running. The same sidebar supports play, reorder, remove, previous/next and automatic advance. Unresolved titles, including the selected row, load serially at lower priority without waiting for playback loading, buffering or quality extraction. YouTube uses a title-only oEmbed request; other sites use yt-dlp metadata and Miruro uses optional episode metadata. Arrival still depends on the site/network; failed lookups retain the supplied label, and full playback metadata takes precedence. Playback sources still resolve fresh when selected or revisited; local-file batches still use natural filename order. yt-dlp items use the original page URL for resume and version-1 progress reports; recognized YouTube video URLs still canonicalize.
 - **Seeking:** click or drag the progress track or thumb to seek. The thumb centers on the cursor, clamped to the track endpoints. While mouse-seeking, the segment under the thumb smoothly thickens and returns to normal on release. Hovering a named segment fades its title in above the segment's center. Reduce Motion disables these transitions.
 - **YouTube chapters:** when yt-dlp provides usable chapters, small rounded gaps mark their boundaries in the playback track. Boundaries use the current player's duration; missing or malformed chapter data leaves ordinary playback unchanged. Chapters do not add opening/ending skip buttons. Availability varies, and description-derived timestamps may differ from YouTube's displayed chapters.
+- **Sponsored ranges:** optional [SponsorBlock](https://sponsor.ajay.app/) sponsor/skip ranges paint the existing track crimson without adding chapter boundaries or changing chapter gaps. Hover shows **Sponsor** alongside any chapter title; accessibility also identifies sponsored ranges. This is visual information only: it never seeks or skips.
 - **Miruro metadata:** titles and opening/ending intervals load independently of playback when available. Small rounded gaps mark interval boundaries in the slider. Inside a segment, **Skip Opening** or **Skip Ending** appears at the top-right below the titlebar for up to ten seconds or until the segment ends; clicking seeks to its end. A light background fill grows as the offer expires, with a short entrance/exit transition; Reduce Motion uses stepped countdown updates without the transition. Ignored offers stay dismissed until the media is closed or replaced. Missing/invalid metadata leaves playback usable, and timings may differ between cuts. Nothing skips automatically.
 - **Resume:** videos resume their saved position; finished videos restart from the beginning. Live and audio-only media do not save progress.
 - **Compact mode:** press **P** for a floating player; double-click it to restore. Drag noninteractive areas to move the window. The queue starts hidden each time you enter compact mode; **⇧⌘L** or **gear → Show Queue** expands it below the video. Its top fade has a 12-point solid section and a 20-point transition, with the first row starting below both. The same shortcut toggles the normal sidebar, whose visibility is preserved when leaving compact mode. Use the titlebar pin to keep the normal window on top.
@@ -82,6 +83,21 @@ Copy the settings you want to change into the config file; omitted settings keep
 
 The queue shortcut can be rebound with `show_queue` and `hide_queue` under `[keys]`; give both actions the same chord to keep a single toggle.
 
+### SponsorBlock
+
+SponsorBlock is **off by default**. Enable **Playback → SponsorBlock → Show Sponsored Ranges** for the session, or opt in at startup:
+
+```toml
+[playback]
+sponsorblock = true
+```
+
+Use `false` (the generated default) or omit the setting to stay opted out; non-boolean values are rejected. The optional lookup runs independently of playback, only for canonical YouTube videos. Failure leaves playback unchanged with no sponsored markers.
+
+Enabling it adds a connection to `sponsor.ajay.app`. Requests use a bucket identified by the first four hexadecimal characters of the video ID's SHA-256 hash, reducing disclosure compared with sending the full ID; this is **not anonymous**. Terebi sends no cookies, account credentials or API key and makes no submissions, votes or view reports.
+
+Ranges require finite, strictly valid bounds inside the actual player duration. A known reference duration that differs from playback by **one second or more** is rejected. Ranges with an unknown reference duration are retained until the player reports an actual finite duration, then validated before display.
+
 ### Miruro providers
 
 Choose **Playback → Miruro → Video Host** or **Caption Provider** in Terebi's menu bar, or use **gear → Miruro**, to change providers for the session. Choices retain both provider and track: `ssub` (soft subtitles), `sub` (hard subtitles), or `dub` (dubbed audio). Video and caption providers are independent; available choices come from the episode response. These menus do not write the config file.
@@ -114,3 +130,9 @@ Native playback supports the returned proxy configuration and HLS query/segment-
 Install FFmpeg for test fixtures (`brew install ffmpeg`), then run `make check`. The suite requires a graphical macOS session and a working audio device; it launches players and plays short test audio. See the [Makefile](Makefile) for individual check targets.
 
 For the focused native compact-queue smoke (transparent, noninteractive app window), run `TEREBI_CHECK_COMPACT_QUEUE_ONLY=1 make check-startup`. `make check-window check-config` covers dropdown geometry, resizing, metadata aspect changes, restoration and configurable queue shortcuts without displaying windows.
+
+`make check-sponsorblock` exercises the bounded native lookup and duration validation with local fixtures; `.build/sponsorblock-check --live` performs read-only public API probes. `make check-resolved` includes SponsorBlock opt-in/failure isolation, same-video cancellation, direct/saved/queue/enqueue launches, quality changes and Miruro separation. The native slider regression (`.build/cast-playback-check --slider-regression`, after building that target) checks crimson painting across chapter gaps, buffering, active emphasis, hover and seeking.
+
+## Acknowledgements
+
+Uses [SponsorBlock](https://sponsor.ajay.app/) data under the [CC BY-NC-SA 4.0 license](https://creativecommons.org/licenses/by-nc-sa/4.0/). Distribution involving this data must account for its **NonCommercial** and **ShareAlike** conditions; obtain separate permission from the relevant rights holders if your intended use needs it. This data credit does not relicense Terebi's application source.