Finish migrating the movement tool into Silphe

[martymcenroe]

The executables were imported into src/silphe/ (the movement model, the calibration game, the analyzers, the arc view). Finish the move.

Remaining

• Confirm everything runs here (silphe-play, silphe-arc, etc.).
• Optionally copy the operator's existing 10 sessions of recordings from the old location so the arc view is populated immediately (local biometric data — operator's call).
• Remove the old working-copy files once verified (untracked there — never committed; confirm before removing).
• Scrub any stale internal references in the code/docs (the science doc is the canonical home now).

Silphe is now its own standalone project.