Type Practice: a typed-answer study mode (FSRS-decoupled)

[bootuz]

Summary

Adds Type Practice, a new study mode where you type the answer instead of self-grading — fully decoupled from spaced repetition.

• Whole-deck, retry-until-correct typed practice that writes zero FSRS state and zero review logs — only its own append-only typing_logs (synced to Firestore like review logs). Spaced repetition scheduling is never touched.
• Answer matching is normalized + accent-sensitive, with an "I was right" override; wrong answers show a char-level colored diff (mint matches / pink misses) of the correct answer vs. what you typed.
• Session direction choice (type the front vs. the back), prompted at session start (session-only state, no persistence); audio plays in both directions.
• Progress surfaces: an end-of-session report (cards, first-try accuracy, best combo, newly mastered) and a per-deck mastery ring derived from latest-first-try-correct.
• Gamified in-session UI: top progress bar + 🔥 combo chip, a prompt hero card, a mint success-flash with auto-advance, and a bottom answer bar that keeps the keyboard pinned for a fast typing rhythm.
• Wrong-answer reveal: the keyboard drops and a result card rises (Azri's own card style — white surface, hairline border, an INCORRECT status pill, color only in the diff), with Continue / "I was right".

Built brainstorm → spec → plan → subagent-driven, with two-stage review (spec compliance + code quality) per task. Specs/plans under docs/superpowers/.

Test Plan

• ./gradlew :app:testDebugUnitTest green (pure domain units: matcher, session state machine, mastery, diff; plus ViewModel virtual-time tests).
• ./gradlew :app:assembleDebug succeeds.
• On device: run a Type Practice session — wrong answer drops the keyboard and shows the result card; Continue brings the keyboard back; correct answer flashes mint and auto-advances without flicker; finish screen shows the report.
• Verify the deck's FSRS due/state is unchanged after a Type Practice session (decoupling holds).
• Verify typing logs sync (append-only) and the per-deck mastery ring reflects latest first-try results.