docs: factory integration grill — decision record, ADRs, and chunk scope update

- Decision record covering 12 decisions from the factory integration grill
- ADR-0008 (factory boundary: this repo is a provider, not a factory instance)
- ADR-0009 (flat skill taxonomy with category metadata in frontmatter)
- ADR-0010 (role skills in .agents/skills/; core/agents/ for subagent definitions)
- Issue 0013 (LESSONS.md at repo root)
- Issue 0014 (docs/spec/ living spec layer + VISION.md refactor)
- ROADMAP Chunk 3 scope expanded: skills rebuild, new skills (session-handoff,
  governance-check, git-guardrails, write-adr), IaC/Gitea global optional
- Per-skill process: implementation guidance Sections 4-5 and skills index
  referenced as starting point before web research and grilling
- factory-research-gaps-conflicts.md marked superseded

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

.agents/skills/write-a-skill/SKILL.md

@@ -1,6 +1,9 @@
 ---
 name: write-a-skill
 description: Create new agent skills with proper structure, progressive disclosure, and bundled resources. Use when user wants to create, write, or build a new skill.
+metadata:
+  category: factory
+  version: "1.1"
 ---
 
 # Writing Skills