Summary

Lifts prefix / type whitelists that were hardcoded across multiple skills, hooks, and CI into a versioned JSON config read through a shared shell library. This is the foundation ticket for the enforcement-hook wave (#107, #110, #111, #112, #113, #114, #115) — they all need a consistent place to read project-level config from.

• New defaults file: .claude/project-config.defaults.json (v1 schema, committed upstream)
• New reader lib: .claude/hooks/_lib-read-config.sh (used by hooks + skills + future)
• New reference doc: docs/project-config.md
• AgDR: docs/agdr/AgDR-0006-project-configurable-ticket-schema.md
• Migrated: validate-branch-name.sh, validate-commit-format.sh, validate-pr-create.sh — now read their whitelists from config
• Doc-updated: /feature, /task, /bug Rules sections reference the config location rather than hardcoding the list

Backward-compat: validate-commit-format.sh previously did ad-hoc reading of a flat commit_types top-level key. That fallback is kept so forks that customised before this ticket keep working without edits.

Merge semantics: shallow at the top level (v1). Teams override by copying a subtree. Deep merge deferred — revisit if pain warrants. See AgDR-0006 for the full rationale, including why the schema lives in .claude/project-config.*.json and not in onboarding.yaml.

Testing

Smoke-tested locally end-to-end against the four migrated consumers:

# 1. Reader library — defaults load, fallback works
source .claude/hooks/_lib-read-config.sh
config_get '.ticket.prefix_whitelist[]'       # → Feature, Bug, Chore, Refactor, Testing, CI, Docs
config_get '.branch.type_whitelist[]'         # → feature, fix, refactor, chore, docs, test, spike, ci, build, perf
config_get_or '.nonexistent.key' 'fallback'   # → fallback

# 2. validate-branch-name.sh — accepts configured types, rejects invented
echo '{"tool_input":{"command":"git push origin HEAD"}}' | bash .claude/hooks/validate-branch-name.sh
# rc=0 on a valid branch

# 3. validate-pr-create.sh — blocks bad type, passes good type
echo '{"tool_input":{"command":"gh pr create --repo X/Y --title \"invented(#109): test\" --body \"## Glossary\""}}' \
  | bash .claude/hooks/validate-pr-create.sh
# rc=2 with message listing accepted types from config

# 4. validate-commit-format.sh — blocks bad type
echo '{"tool_input":{"command":"git commit -m \"invented: test\""}}' \
  | bash .claude/hooks/validate-commit-format.sh
# rc=2

# 5. Zero-config fallback — hooks still work on a fresh checkout
# Verified by the inline default regex in each hook

No CI-level tests added; the config-reader lib is covered by downstream hook tests (added in #110 and #115). A dedicated test fixture for the lib itself would be a nice-to-have follow-up.

Scope — what this does NOT do

• Does not change the existing shipped defaults (same six ticket prefixes, same eleven commit types). Behavioural diff is zero for a fresh fork with no .claude/project-config.json override.
• Does not deprecate the legacy flat commit_types key. That's a separate follow-up once adoption is measurable.
• Does not introduce schema validation (JSON Schema or similar). Malformed config degrades gracefully — reader returns null, hooks fall back to shipped defaults.

Glossary

Closes #109