Harry Bayliss
2f109a84fa
Added a full ASCII-video benchmark suite that hammers the renderer with 30 KiB / 70 KiB full-screen frames at 30, 60, and 120 fps targets — both renderer-only and full-pipeline (em.Write + renderer + stdout). Each stream benchmark reports µs/frame, fps_ceiling, and percent of the per-frame budget consumed. The pipeline benchmarks revealed we were missing 120 fps by a wide margin (190%-350% of budget at 120fps, 60-90 fps ceiling). Isolating em.Write confirmed libghostty-vt is the bottleneck — 16-29 ms per truecolor frame, library file at 33 MiB. Root cause: the Makefile invoked `zig build` with no -Doptimize, and Zig's standardOptimizeOption defaults to Debug. So the shipped libghostty-vt was unoptimised. Fixed by pinning ReleaseFast in the Makefile (override via GHOSTTY_VT_OPTIMIZE for debug builds of the upstream lib). Existing checkouts need `make clean-deps && make deps` to pick up the rebuild.