feat: wire factory principles into content index and write-skill governance check

- AGENTS.md: add factory principles and factory-integration-decisions to
  on-demand content index so they are discoverable for skill design work
- write-skill: insert conflict-check step (step 3) — sub-agent reads
  constitution and factory principles after grill, before any writing;
  hard gate with explicit self-check item; renumber steps 3–8 → 4–9
- META.md: bump to v1.4

Closes the gap identified in PRD chunk-3-skills-library §sub-agent-usage:
conflict checking against constitution and factory principles was specified
but never wired into the write-skill process.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

AGENTS.md

@@ -23,6 +23,8 @@ Read these on demand:
 - `docs/ROADMAP.md` — chunk status table and open questions; read this to orient on where work stands
 - `docs/adr/` — architectural decisions; read before answering design questions or proposing structural changes
 - `docs/ai-constitution.md` — full governance evidence base; read when a governance decision needs justification
+- `docs/research/ai-coding-factory/ai-coding-factory-principles.md` — factory design rationale; read when implementing, auditing, or reviewing skills or factory structure
+- `docs/notes/factory-integration-decisions.md` — decisions from the factory integration grill; read when making skill authoring or factory design decisions
 - `docs/HUMANS.md` — human practitioner checklist; applies when working with AI tools in this repo
 - Governance rules are always in effect — `core/instructions/governance.md` (agent rules); `docs/research/governance_principles/CONTROLS.md` (Phase 2 enforcement spec, Chunk 6)