Outlier score badge on YouTube thumbnails

Scores every card against the median views of its own channel's last N
videos, badging the thumbnail above the duration stamp. Shorts and regular
videos are scored in separate pools, live streams in none. Baselines come
from YouTube's InnerTube endpoint, one request per channel, cached a day.
Interface in English and Turkish.

README.md

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+# Outlier Badge
+
+[Türkçe](README.tr.md)
+
+A Firefox extension that puts an outlier score on the corner of every YouTube
+thumbnail. Score = the video's views divided by the **median** views of its
+channel's last N videos. The median is a deliberate choice: a single viral video
+would drag a mean upward and make everything else on that channel look like it
+never outperformed. Shorts are scored against the channel's Shorts, regular
+videos against regular videos, and live streams enter no pool at all. The watch
+page also gets a panel with the score's details and the channel's recent view
+distribution.
+
+No server, no API key, no account: the extension calls YouTube's own internal
+(InnerTube) endpoint from inside youtube.com, without session credentials. One
+request per channel, cached in `storage.local` for 24 hours by default, and cards
+are only processed once they scroll into view.
+
+## Trying it out
+
+`about:debugging#/runtime/this-firefox` → **Load Temporary Add-on** → the
+`manifest.json` in this directory. It disappears when Firefox closes.
+
+## Installing it for good
+
+Release Firefox refuses to permanently install an unsigned add-on. Getting it
+signed is free and shows the extension to nobody:
+
+1. Create an account at addons.mozilla.org/developers and grab a JWT issuer and
+   secret from **Manage API Keys**.
+2. Sign the package (inside a container so npm never touches this directory):
+
+   ```
+   podman run --rm -v "$(pwd)":/w:z -w /w docker.io/node:alpine \
+     npx --yes web-ext sign --channel=unlisted \
+     --api-key=JWT_ISSUER --api-secret=JWT_SECRET
+   ```
+
+3. Install the resulting `web-ext-artifacts/*.xpi` through `about:addons` → gear
+   icon → **Install Add-on From File**.
+
+The signature is tied to the add-on id in `manifest.json`, so leave that id
+alone. Every new signature needs a bumped `version`, and unlisted add-ons do not
+auto-update: when you change the code you sign and install it again. If you would
+rather skip signing altogether, Firefox Developer Edition and Nightly honour
+`xpinstall.signatures.required = false` in `about:config`, but release Firefox
+ignores that setting.
+
+## Using it
+
+The toolbar icon opens the settings: turn badges off, skip Shorts, pick the
+baseline size (last 15/30/60/90 videos), hide scores below a threshold, set the
+cache lifetime, choose the interface language, and clear the cache. The same
+popup reports how many cards were scanned and scored in that tab, which is where
+you look first when a badge fails to appear. The interface is available in
+English and Turkish, following the browser's language by default.
+
+To exercise the parsing and scoring logic without opening a browser, run
+`node test/check.js` (it makes one real channel call too).
+
+## Known limits
+
+- YouTube hands out rounded view counts ("1.2M views"), so the score is an
+  approximate ratio rather than an exact one.
+- Videos under 7 days old have not gathered their views yet and score lower than
+  they deserve. The dot next to the badge marks them.
+- The baseline is the channel's last N videos, not its whole history. On a
+  growing channel an old video scores higher than it should.
+- Members-only videos never expose their view counts, so they neither join a
+  baseline nor get a score.
+- With fewer than 3 videos left in the pool no score is computed and no badge
+  appears.
+- InnerTube is an unofficial interface. If YouTube renames its fields the badges
+  disappear; the page itself keeps working.
+
+There is **no** views-over-time chart, because YouTube publishes no historical
+view data for any video. vidIQ, Social Blade and everyone else build that curve
+from snapshots they collect themselves; in a single-user extension it would take
+months to appear and only for videos you personally opened. The watch page panel
+shows the two things that work without waiting instead: where the video sits in
+its channel's distribution, and its average views per day.