ci: add CI and release workflows

[0xLeif]

Summary

• Adds .github/workflows/ci.yml — build + test on Linux/macOS/Windows, clippy with -D warnings, rustfmt --check
• Adds .github/workflows/release.yml — cross-compile binaries on tag push, attach to GitHub release
• Applies cargo fmt to make the lint job pass

Test plan

• CI workflow runs green on this PR
• Future tag push produces release artifacts for all 4 targets

🤖 Generated with Claude Code

[corvid-agent]

👋 CorvidAgent is looking into this.

[corvid-agent]

Looks good — clean CI/CD setup. A few minor observations:

CI (ci.yml)

• The check job uses cargo build --release which is slower than a debug build. For CI purposes a plain cargo build would catch the same compilation errors faster. Reserve --release for the release workflow.
• Lint-only-on-ubuntu is the right call since clippy/fmt results are platform-independent.

Release (release.yml)

• No test step before building artifacts. If a tag lands on a broken commit, you'd ship broken binaries. Consider either adding cargo test before the build step, or requiring CI to pass on the tagged commit (e.g., via branch protection on main + only tagging from main).
• x86_64-apple-darwin on macos-latest (ARM runner) relies on cross-compilation — should work fine since the target is explicitly installed via dtolnay/rust-toolchain, but worth a sanity check on the first release.

Source changes — purely cargo fmt, no logic changes. ✅

Overall solid. Approving — the suggestions above are minor improvements, not blockers.

[gemini-code-assist]

Code Review

This pull request primarily focuses on code formatting within src/main.rs, including expanding the Kind::all array to multiple lines and condensing a timeout calculation and a test assertion into single lines. A review comment suggests using assert_eq! instead of assert!(matches!(...)) in the test suite to improve the clarity of error messages during failures.

[gemini-code-assist]

In tests, using assert_eq! is generally preferred over assert!(matches!(...)) for simple equality checks. assert_eq! provides more descriptive error messages by displaying both the actual and expected values upon failure, which is particularly helpful when debugging CI failures in a headless environment.

Suggested change

	assert!(matches!(game.board[(H - 1) as usize][0], Some(Kind::T)));
	assert_eq!(game.board[(H - 1) as usize][0], Some(Kind::T));