chore: prepare production rust release

CONTRIBUTING.md

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+# Contributing
+
+## Checks
+
+Run these before pushing:
+
+```bash
+cargo fmt --check
+cargo test --locked
+cargo clippy --locked -- -D warnings
+cargo build --release --locked
+```
+
+## Style
+
+- Keep the application single-binary and Rust-first.
+- Keep config backwards-compatible where possible.
+- Prefer explicit, small functions over hidden behavior in the TUI.
+- Do not add runtime dependencies on Python, Node, or external services.
+
+## Commits
+
+Use concise conventional commits where practical:
+
+```text
+feat: add timer progress gauge
+fix: wrap preview commands on narrow terminals
+chore: release v1.1.1
+```