Make Conventional Commits (type(scope): description) the canonical
commit and PR-title format across Sea Haven, replacing the previous
imperative/capitalized/no-prefix rule.
- commit-messages.md: full rewrite to the type(scope): description
format with the type table, lowercase/imperative description rules,
breaking-change (! + BREAKING CHANGE footer) guidance tied to SemVer,
and updated template and examples.
- git-workflow.md: extend the branch-prefix table with chore/, docs/,
refactor/, and release/ (alongside the existing feature/bug/hotfix),
mirroring the commit types.
- pull-requests.md: reconcile the title rule to the Conventional Commit
format.
- README.md: update the commit-messages one-line summary.
Refs: INFRA-57
