feat: escape cancel countdown with 3-second progress bar

[rsslldnphy]

Summary

• Pressing Escape during recording now shows a "Cancelling..." HUD with a draining orange progress bar (3 seconds) instead of immediately switching to transcribing
• Second Escape during the countdown reverses the decision → transitions to "Transcribing..." and pastes normally
• Countdown expiry → HUD disappears silently, transcription runs in the background, result saved to log with wasPasted = false (no paste triggered)
• Short recordings (< 0.5 s) skip the countdown and are silently discarded as before
• Transcription failures after a cancelled recording are silently discarded with no notification

Changes

• AppState.cancelling — new state with transitions recording→cancelling, cancelling→processing, cancelling→idle
• IndicatorState.cancelling — new HUD state with orange label + CABasicAnimation fill bar (sublayer-based to avoid Auto Layout conflicts)
• TranscriptionLogEntry.wasPasted: Bool — backward-compatible (absent JSON key → true)
• TranscriptionLogStore.append(wasPasted:) — new parameter with default true
• AppDelegate — beginCancelCountdown(), restoreFromCancelling(), commitCancelledTranscription(), silentlyResetToIdle(); cancelRecording() removed
• LogView — "not pasted" caption annotation on cancelled entries

Test plan

• Record dictation → press Escape → verify "Cancelling..." HUD with draining orange bar appears
• Let countdown expire → verify HUD disappears, no text is pasted, entry appears in log with "not pasted"
• Record dictation → press Escape → press Escape again → verify HUD switches to "Transcribing...", result is pasted, log entry has no "not pasted" annotation
• Record < 0.5 s → press Escape → verify no countdown shown, silent discard
• Normal hotkey flow (no Escape) → verify zero regressions
• swift test → 131 tests, 0 failures

🤖 Generated with Claude Code