Move skip detection to a server, and find that it detects ads

The server is Peter's design and it works: listend polls the phone's feed
list, mirrors the newest 8 episodes per show, detects across all of them at
once, and serves the offsets *and the audio they belong to*. Deployed on
tungsten behind Apache at https://listen.terst.org. FingerprintWorker and
MidrollWorker are deleted -- the battery drain is gone because the work is.

Serving the audio is load-bearing. Dynamic ad insertion turned out to be on
every episode: Grass Apes declares 22:05 and the server was served 28:18. An
offset measured on one copy is minutes wrong for another, so the phone has to
play the bytes the detector examined. The offsets land in the same columns the
on-device detector wrote, so playback needed no changes and there is no
migration.

**The headline finding is a failure, and it is proved rather than suspected.**
Detection reported the intro confirmed on 8 of 8 Radiolab episodes and passed
its self-check. It had locked onto an advertisement. The chosen segment was
searched for in an ad-free copy of the same episode fetched hours earlier:
r = 0.0621. It is in the ad break, not the programme.

The confirmation threshold assumes three *independently fetched* episodes.
Mirroring 8 within one minute from the same ad server makes them maximally
dependent -- whatever campaign is running is in all of them, identical -- and
SelfCheck cannot catch it, because the segments genuinely are the same audio.
Moving to a server fixed the cost problem and broke the independence the
safety mechanism rests on. The published offsets are head-window matches, so
they happen to skip pre-roll advertising, which is useful by accident and will
move whenever the campaign rotates. It is not intro detection and is not
described as such anywhere.

The fix, not made: record when each episode was fetched and require the
agreeing episodes to span more than one fetch occasion. Reasoning, and an
argument for detecting the ads directly instead, in docs/detection-findings.md.

Also recorded there: two tooling traps that each cost real time. `android-ui
tap` can land on the soft keyboard, because the dump reports layout
coordinates the IME does not move -- a Save button and a text field both
appeared tapped and neither fired. And the server's token is alphanumeric now
because `adb shell input text` ate the leading "-" of a base64url one and
produced a silent 401 that looked like broken wiring.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AwnALZL6bD4VBtATDVv3B

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