fix(input): restore fast Shift double-tap

[AsafMah]

Summary

• restore Caps Lock for legitimate fast Shift double-taps, including taps less than 100 ms apart
• require an intervening Shift release before treating another press as a double tap, preserving protection against duplicate pointer-down/key-repeat delivery from Capslock is activated with a single tap LeanBitLab/LeanType#186 and CAPS Lock get activated with single tap. LeanBitLab/LeanType#188
• cover fast and ordinary double-taps, single tap, duplicate presses in both pressing states, post-chord timing, and normal Caps Lock unlock
• report the inherited regression upstream as Fast double-taps on Shift no longer enable Caps Lock LeanBitLab/LeanType#475

Fixes #146

Test evidence

• Pre-fix: KeyboardStateTest completed 5 tests with 2 failures: fastDoubleTapShiftLocksCaps and duplicateShiftPressWithoutReleaseDoesNotLockCaps
• Targeted after final rebase: :app:testOfflineDebugUnitTest --tests '*KeyboardStateTest' --rerun-tasks passed all 8 tests
• Compile: compileOfflineRunTestsKotlin passed
• Authoritative gate: 371 tests, 4 expected Windows ParserTest failures, 8 skipped; [ok] no new failures against baseline (--started-after 1788446191)
• Independent review: release-boundary invariant accepted; every requested edge case is covered

Device verification

SM-S936B was unavailable: both adb devices -l and adb mdns services were empty. Manual verification remains:

1. Single-tap Shift and confirm temporary Shift only.
2. Double-tap Shift quickly and confirm Caps Lock plus the locked Shift icon.
3. Type several letters and confirm all are uppercase.
4. After the 300 ms double-tap window, tap Shift once and confirm Caps Lock unlocks.