fix: seek bar follow-ups from the PR #59 review

[chrisuthe]

Summary

Closes out the remaining suggestion-level findings from the PR #59 review.

• Static-delay-free display anchor: IClockSynchronizer.ServerToClientTime subtracts the configured static delay (audio-scheduling semantics). The seek bar anchor now adds it back so the displayed position reflects measurement time — a positive delay no longer runs the bar ahead, and a negative delay no longer pushes every conversion into the future, which permanently tripped the plausibility guard so the server-timestamp anchoring path silently never engaged.
• Collision-proof track identity: identity is now a (title, artist, album) tuple instead of a |-joined string, eliminating delimiter collisions; a Debug log flags degenerate (fully untagged) identities where identity-based resets cannot distinguish consecutive tracks.
• Boundary pins (test-only): exact 5 s anchor-age boundary, negative playback_speed clamped to 0 (bar never runs backwards), negative progress/duration clamped to 0.
• claude.md drift fixes (pre-existing staleness): protocol table now describes group/update accurately and gains the missing server/state row; ServerToLocalTime → ServerToClientTime; SendSpinHostService/SendSpinClient → actual class names SendspinHostService/SendspinClientService.

Testing

• TDD: the static-delay and identity-collision tests were written first and confirmed failing against the previous behavior (bar at 120.6 s instead of 120.2 s with a 400 ms delay; colliding identities skipping the reset).
• Tracker suite: 36/36 pass (30 existing + 6 new). Full suite: 133/135 — the 2 failures are the known pre-existing resampler-area ones, unchanged.
• Release rebuild: 0 errors, warning count exactly at the 553 baseline.