feat(review): summarize team coverage

[pierrick-fonquerne]

What changed

Adds a compact coverage table to complete and incomplete team-review comments. It reports specialist roles planned, completed, unavailable, and the total number of coverage gaps.

Safety

A specialist role that fails any batch is unavailable and is excluded from the completed count.

Validation

• cargo test --manifest-path tools/ai-review/Cargo.toml review::tests
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-features --no-fail-fast
• cargo build --release