feat(review): make human output easier to scan

[forhappy]

Summary

• shorten commit, report, and finding references in review text and Markdown
• lengthen compact references deterministically when prefixes collide
• render machine-style statuses and gate names as plain language
• replace opaque witness endpoint hashes with concise relationship summaries
• apply the same readability policy to readiness Markdown

Canonical JSON and SARIF are unchanged and retain full revision IDs, fingerprints, graph identities, and witness evidence.

This is the readability follow-up to merged PR #310.

Verification

• cargo fmt --all -- --check
• cargo test -p compass-output --test pr_review --locked
• cargo test -p compass-output --locked
• cargo test -p compass-cli --test review_cli --locked
• cargo clippy -p compass-output --all-targets --all-features --locked -- -D warnings
• cargo clippy --workspace --lib --bins --locked -- -D warnings
• cargo test --workspace --lib --bins --locked
• cargo test -p compass-cli --test compass_product --locked
• sh scripts/check_product_boundary.sh