Add compiled clip playback with shared timing semantics

[Hancapo]

Summary

• Add YcdClipAnimation.compile() and public YcdClipSampler with typed phase/time evaluation methods.
• Share time-to-frame conversion with mutable clips; preserve current clamping, loop metadata and caller-owned phase/rate behavior without introducing new timing semantics.
• Document lifetime, memory, mutable edits, concurrency and per-track filtering.
• Add clip timing/seeking tests, repeatable performance cases and an opt-in loose-YCD differential corpus test.

Verification

• The complete indexed name-linked CUT animation corpus was compared: 10,275 Enhanced YCD records with 195,904 animation clips, and 9,127 Legacy records with 179,030 animation clips. Counts include archive variants. Maximum component difference at the tested positions was 0.0.
• Comparisons cover integer/fractional times, physical sequence boundaries, missing-track/unit cases and clip endpoints/seeks. More than 234 million typed values were compared across both editions.
• The 27 clips in pro_mcs_5-0, evaluated over 180 frames, improved from 1.229 s to 0.136 s in Enhanced and 1.227 s to 0.127 s in Legacy (library-only measurement).
• The opt-in loose-resource integration test also passed with direct retail resources from both editions.

Based on #298. No consumer application edits or release. These are sampled differential results and library timings, not a renderer FPS or in-game certification claim.