feat(config): expand role_registry + fix T4 default runtime
Role registry additions:
- T2: add ai, security, mobile domains
- T3: add data, ai, security, mobile, database, devops, docs domains
- T4: add data (data-engineer), embedded (firmware-engineer)
- T5: add accessibility, e2e, frontend, data verifier roles
TeamRunner consistency fix:
- T4 briefs now default to 'coding_agent' runtime (Claude Code)
per build spec: 'Claude Code as default T4 runtime'
T3 can still override preferred_runtime per task
Hans Heinemann
d02faf5cac