v0.0.15

Fixes

• Fix 11s local-hit regression — tmutil addexclusion was being called per-crate (300+ times per build) since v0.0.10, causing every local cache hit to take ~11 seconds instead of <100ms. Moved to the daemon which runs it once.
• Cache rustc --version and cc --version — file-based cache keyed by binary mtime eliminates 600+ subprocess spawns per parallel build.
• Add SQLite busy_timeout — prevents SQLITE_BUSY failures when 300+ wrapper processes hit the database concurrently.
• Fix prefetch race condition — use flock so only one wrapper process per build session sends the prefetch hint (was producing 9+ duplicate requests).
• Reduce log noise — broken-pipe warnings from fire-and-forget clients downgraded to debug level; also handles macOS EPIPE reported as ErrorKind::Other.