fix(input): preserve Win16 flipper key latches

Normal ball-end handling keeps the original flipper key bytes and geometry
unless the current player has finished. Rust instead reset both flippers on
every drain, skipped the normal WAVE 2021 release edge, and treated a key still
held after Tilt as a fresh press once Tilt cleared.

Preserve flipper state across ordinary drains. Tilt and a player's final ball
now clear only the key flags, let the timer epilogue lower raised geometry, and
latch each physical key until key-up before accepting another press. This
matches the original WM_KEYDOWN/WM_KEYUP lifetime while retaining modern
per-frame input sampling.

Test Plan:
- `cargo test --workspace --all-targets --all-features` -- 119 passed
- `cargo clippy --workspace --all-targets --all-features -- -D warnings` -- passed
- `rumdl check --flavor commonmark RECONSTRUCTION.md CHANGELOG.md` -- passed
- `git diff --cached --check` -- passed

tdkpin-rs/CHANGELOG.md

@@ -147,6 +147,10 @@ and this project adheres to
   Left-Shift, keypad-3, and Space formulas using scalar 15, the shared Borland
   random stream, 32-bit velocity wrapping, and the decaying 16-bit `+25` tilt
   counter with its randomized `30..39` threshold.
+- Preserve held flipper keys and raised geometry across ordinary drains. Tilt
+  and a player's final ball now clear the key latch, release a raised flipper
+  through its normal WAVE 2021 timer edge, and require physical key-up before
+  the same key can raise it again.
 - Replace the Xorshift gameplay RNG with the original Borland linear stream and
   unbiased `Random(n)` high-word mapping. Launcher variation, effect selection,
   claw terminals, and magnetic-field impulses now share the recovered sequence.