feat(factory): add Factory Pi workflow skill

BUILD_PLAN.md

@@ -69,9 +69,9 @@
 
 **Implementation files:** `skills/factory/SKILL.md`, optional `prompts/factory-start.md`, package manifest registration if Pi discovery requires it; validate exact installed Pi behavior.
 
-- [ ] Write the skill using `docs/WORKFLOW.md`; explain what the CLI does, when to use it, and when to stop for a real decision.
-- [ ] Load it in Pi, invoke it explicitly and automatically, and confirm it uses existing commands rather than narrating a fictional `/factory run`.
-- [ ] Publish CP-05 as a testable task in Factory's own backlog, then observe real Firstmate dispatch and closure. **Gate:** F-09 and the first real task/worker trace. Dogfooding remains unproven if only task publication succeeds.
+- [x] Write the skill using `docs/WORKFLOW.md`; explain what the CLI does, when to use it, and when to stop for a real decision.
+- [x] Load it in Pi, invoke it explicitly and automatically, and confirm it uses existing commands rather than narrating a fictional `/factory run`.
+- [x] Publish CP-05 as a testable task in Factory's own backlog, then observe real Firstmate dispatch and closure. **Gate:** F-09 and the first real task/worker trace. Dogfooding remains unproven if only task publication succeeds.
 
 ## CP-05 — Evidence and independent completion