feat(study): synchronized RSVP + audio reader (--study mode)

[DavidTbilisi]

Summary

• Adds tts-ka --study — a synchronized RSVP word-flash + audio playback window driven by the per-word timing list fast_audio.generate_audio_with_subs already emits.
• Five new modules + three test files; no rewrite of existing TTS paths.
• Quiz generation is intentionally a swappable QuizProvider Protocol; the default RuleBasedProvider._generate_for_chunk is a TODO(human) slot left for a follow-up commit.

Architecture

Module	Purpose
study_session.py	Pure-logic timing model: bisect_right lookup over a precomputed start_ms array → O(log n) inside the 30 Hz sync loop.
study_player.py	Tk + lazy-imported pygame window; centred big-word label + faded peripheral context. Excluded from coverage (matches gui.py).
quiz.py	QuizProvider Protocol, RuleBasedProvider (zero-dep, _generate_for_chunk is the TODO slot), LLMQuizProvider stub for future swap.
session_log.py	Append-only JSONL at ~/.tts_ka_study.jsonl (env override TTS_KA_STUDY_LOG); malformed lines skipped, not raised.
main.py patch	--study and --study-chunk-words flags; lazy import so non-study users do not pay the pygame cost.

CLI

pip install -e ".[study]"
tts-ka --study --study-chunk-words 200 -l en file.txt
tts-ka --study cb -l en      # use clipboard text

Why this exists

Reading speed for non-fiction is bottlenecked by two independent axes — language-processing speed and eye mechanics. This mode trains the language-processing axis by pairing RSVP visual flash with audio playback of the same text, so the bottleneck cannot hide behind the other channel. The session log gives a longitudinal WPM trajectory for later analysis.

Test plan

• pytest tests/test_study_session.py tests/test_quiz.py tests/test_session_log.py — 30 new tests pass
• Manual: tts-ka --study cb -l en with a paragraph of English in the clipboard; verify audio plays and the big-word label tracks
• Manual: hit "Quiz me" mid-playback and confirm the popup surfaces NotImplementedError cleanly (until the TODO is filled)
• Manual: hit "Save session" and confirm a JSONL line lands at ~/.tts_ka_study.jsonl
• Manual: tts-ka --study cb -l ka with Georgian text to verify the cross-language path
• Follow-up PR: implement RuleBasedProvider._generate_for_chunk and update test_calls_into_todo_slot to assert real Question shape

🤖 Generated with Claude Code