Delete on-device detection. Detection is the server's

Peter's call: server first. The audio-fingerprint subsystem ran on the phone until detection moved
to the server, and then kept being shipped: FingerprintWorker and MidrollWorker went at the time
and the twelve classes they drove stayed, unreachable, in every APK since. ReachabilityTest found
it on 2026-11-03 once it was widened to classes, and it has been sitting in that test's allowlist
with its reasoning since.

Gone: IntroOutroDetector, AudioCorrelation, MidrollScanner, MidrollDetector, MidrollUpdater,
FingerprintUpdater, MediaCodecClipSource, Decimate, Fft, MonoResampler, PcmCodec, StoredClip, and
the 67 unit tests over them. 3,092 lines.

**Recoverable by name, not by archaeology.** The tag `on-device-detection` marks the last commit
that has it, pushed to the local remote along with everything else from this session, and the tag
message says how to bring it back. The work cost weeks and the approach may be wanted again.

What stayed, because none of it is detection: SkipSummary words the readout, BreakTrack and
BreakPopup draw and explain the timeline's marks, and MidrollClipStore shrank to deleteAllFor
alone -- its write and read halves had one caller each and both were the deleted updater, but a
phone that ran the old version still has clip files on disk and unsubscribing is the only thing
that clears them. Its test now writes the old layout by hand, because that layout is a
compatibility concern now rather than this class's own choice.

IntroOutroDetector.CONFIRM_THRESHOLD and MidrollDetector.CONFIRM_THRESHOLD moved to SkipSummary,
the only thing left that reads them. Both were three and the server's DefaultConfirmThreshold is
also three, checked against each other before the move.

**The database was deliberately not touched.** show_fingerprints, show_midrolls and
episode_midrolls are the server's columns now -- ServerSkips writes its answers into exactly the
columns the on-device detector used to, which is why playback needed no changes when detection
moved. Four MidrollDao methods went because they were the discovery half (upsertCandidate,
deleteCandidate, getUncheckedDownloaded, setMidrollCheckedAtMs) and the reachability check named
them; a DAO method is not schema, so there is no migration here and nothing for a real library to
go wrong over.

Two things found while doing it, neither caused by it, both written up in CLAUDE.md:

- **The per-show "Detected skips" readout can never say anything.** It reads candidate and
  confirmation rows, and nothing has written one since detection moved -- the server writes
  per-episode ranges and offsets instead. Verified on the emulator, not inferred: a fresh install
  with a live subscription shows "Nothing found yet / Nothing found yet / None found yet" while the
  server is finding and publishing breaks for that very show. It has been lying since the
  migration; deleting the detector only makes it undeniable.
- **RetentionSweeper's pending-episode guard protects nothing**, for the same reason: nothing sets
  a pending basis any more, so both id sets are always empty.

The APK barely moves -- 110KB of dex, 72.61MB to 72.50MB -- because it is dominated by the
embedded Python. This was never going to be a size win and is not being sold as one; it is 3,092
fewer lines to read, search and mislead.

1004 tests pass, detekt 0, lint clean. Coverage 95.35% -> 94.58%, which is the documented
COVERAGE_EXCEPTION case: deleting dead code that happened to be well covered.

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

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