Contributing to type-cli

Workflow

Read docs/PROGRESS.md first to see the current state (Done / Missing / Now).
Work in small, testable increments. Prefer TDD for pure logic (see below).
Before committing: cargo fmt --all, cargo clippy --all-targets -- -D warnings, cargo test.
Update docs/PROGRESS.md at the end of your session (the ritual in CLAUDE.md).
Use Conventional Commits (feat:, fix:, docs:, refactor:, test:, chore:).

engine/ and stats/ are pure: no ratatui/crossterm/I/O, and no Instant::now() — time is passed in as elapsed: Duration. This keeps tests deterministic and Phase 3 ghost-replay simple.
No crossterm outside input.rs and main.rs. Keystrokes become Actions in input.rs.
ui/ never mutates state — it's a pure render of &App into a Frame.
Index text by grapheme, never by byte.
Any change to the stack or a core boundary needs a new ADR in docs/adr/.

Pure modules (engine, stats, sources::normalizer) are unit-tested first: write a failing test for the rule, then implement it. Tests are colocated in each module under #[cfg(test)].
tests/ holds integration tests: full typing sessions, the import normalizer on real fixtures, and (from Phase 2) migrations from an empty database.
Metrics are tested by injecting elapsed — never by sleeping.
UI is smoke-tested with ratatui's TestBackend where useful.

A theme: drop a *.toml in assets/themes/ (embedded default) or in your config dir (override).
A test preset: edit [[presets]] in config.toml.
A challenge source: implement the Source trait in src/sources/.