feat(testing): add deterministic mechanics capture

Add named launcher, flipper, and claw scenarios that advance at exact 120 Hz steps with stable seeds. Emit per-step JSON state/event traces and optionally capture the logical 640x460 framebuffer at any requested time or step.

Cover parser behavior, deterministic replay, launcher timing, flipper edges, and complete capture/release/idle cycles for all claw terminals.

Test Plan:
- cargo fmt --check
- cargo test
- cargo clippy --all-targets --all-features -- -D warnings
- cargo run -- --simulate claw-6 --at 0.15 --screenshot /tmp/tdkpin-sim-validation/claw-6-after-flush.png --trace /tmp/tdkpin-sim-validation/claw-6.json
- Inspect both generated 640x460 PNGs and JSON traces
- git diff --cached --check

tdkpin-rs/README.md

@@ -31,6 +31,22 @@ development packages are also required (X11, OpenGL, and ALSA). Windows needs
 no extra runtime installation; macOS builds with the normal Apple developer
 command-line tools.
 
+## Deterministic mechanics validation
+
+Named scenarios can be advanced without waiting in real time. The simulator
+uses exact 120 Hz steps, prints its final state as JSON, and can write both the
+complete step trace and the original-size 640x460 framebuffer:
+
+```sh
+cargo run -- --simulate claw-6 --at 0.15 \
+  --trace /tmp/claw-6.json \
+  --screenshot /tmp/claw-6.png
+```
+
+Use `--step N` instead of `--at SECONDS` to reproduce one exact update. The
+available scenarios are `launcher`, `flippers`, `claw-1`, `claw-6`, `claw-7`,
+and `claw-18`; `--seed N` fixes random choices for later seeded scenarios.
+
 ## Original and modern controls
 
 | Action | Original key | Additional modern key |