migrate backend to zig 0.16, frontend improvements
backend: zig 0.15 → 0.16 (zat v0.3.0-alpha.7, zqlite master)
- Io.Threaded with explicit io passing (no debug_io hack)
- Io.Mutex, Io.Timestamp, Io.net, smp_allocator
- thread-per-connection replaces Thread.Pool
- Dockerfile updated to zig 0.16.0-dev.3059
frontend: handle autocomplete, layout/styling updates
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>