Context

`validate-commit-format.sh` (shipped in #13) enforces a fixed type list: `feat, fix, refactor, test, docs, chore, style, perf, build, ci, revert`. This matches the PR-title regex in `git-conventions.md` and covers most teams, but some projects want different types:

• Teams that use `wip` as an interim commit type
• Teams that want `security` or `deps` as dedicated types
• Teams that don't use `revert` or want to force squash-merges and therefore forbid it
• Teams using custom conventions like `[MINOR]` / `[MAJOR]`

Currently, changing the type list requires editing the hook script directly. This ticket adds a project-config override so forks can customize without touching framework code.

Acceptance Criteria

• `.claude/project-config.json` schema gains a `commit_types` field (JSON array of strings).
• `validate-commit-format.sh` reads the field from `.claude/project-config.json` if it exists, falls back to the default 11-type list otherwise.
• Same project-config file is also read by `validate-pr-create.sh` if that makes sense — OR keep them independent (PR titles vs commit messages may legitimately have different vocabularies). Decide in the implementation and document in the PR body.
• `.claude/skills/onboard/SKILL.md` — update the discovery questions to ask about commit types (optional, default "use the framework's 11-type list").
• `.claude/hooks/README.md` — document the override in the commit-format hook section.
• Smoke test: project-config with `{"commit_types": ["wip", "feat", "fix"]}` accepts `wip: scratch` and rejects `refactor: cleanup`.

Non-goals

• Does NOT change the default type list.
• Does NOT add support for Conventional Commits breaking change markers (`feat!:`) — separate ticket.

Links

• Root-cause: [Chore] audit CLAUDE.md and mechanize MUST rules into hooks #13 (closed)
• AgDR-0001 mentions `commit_types` as a follow-up