docs: issue 0016 — skill implementation workflow grill

Produces docs/notes/skill-implementation-workflow.md with agreed conventions
for all Chunk 3 skill issues (0017–0028). Key decisions:

- Per-skill process: source discovery (sub-agent) → source review with
  licence/security check (sub-agent) → conflict check vs constitution +
  factory principles (sub-agent) → synthesis grill → co-write iteratively
- Bootstrap: write-eval (hand-written) → write-skill (hand-written) →
  write-docs (first factory-authored, phase 2 of 0018) → everything else
- Upstream review changed from per-chunk-start to per-skill
- `when:` and `references:` frontmatter fields added to authoring standard
- Sub-agent usage prescribed as named steps in the workflow
- HITL: human reviewed and approved conventions

Updates: PRD implementation decisions; issues 0016–0028 with specific
acceptance criteria; docs/spec/overview.md; ROADMAP Chunk 3 housekeeping note
(bootstrap order, cadence, acceptance criteria status); CONTEXT.md Source field
(per-skill cadence, references: companion field); LESSONS.md with three patterns
from the grill session.

Post-grill additions (same session): Step 6 (session handoff) added to the
workflow; handoff section appended to issue 0016; handoff checklist item added
to Chunk 3 closure issue (0028).

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

docs/issues/0018-factory-write-skill.md

@@ -5,19 +5,31 @@
 
 ## What to build
 
-Build `write-skill` — the second bootstrap skill, immediately after `write-eval`. Once `write-skill` exists, it is used to author all subsequent SKILL.md files in Chunk 3 rather than writing them by hand.
+### Phase 1: `write-skill`
+
+Build `write-skill` — the second bootstrap skill. Once complete, it is used to author all subsequent SKILL.md files in Chunk 3.
 
 **Trigger description** (from skills index): "Write a new skill for X, create a SKILL.md that does Y"
 
 **Key constraints:**
-- Produces a complete SKILL.md following the authoring standard (frontmatter, role, when/when-not, required inputs, constraints, process, output format, failure handling)
-- Validates trigger description against three test queries (explicit, implicit, negative) before completing
+- Produces a complete SKILL.md following the authoring standard in `docs/notes/skill-implementation-workflow.md`
+- Validates trigger description against explicit, implicit, and negative test queries before completing
 - Flags if the proposed skill overlaps with an existing skill in the library
 - Skill file: `.agents/skills/write-skill/SKILL.md`; `metadata.category: factory`
-- Origin: new skill (check upstream for prior art during implementation); `source:` populated only if upstream content is adopted
+- SKILL.md is hand-written (write-skill cannot author itself before it exists)
 - Eval via `write-eval` (issue 0017)
 
-Process: upstream review → trigger-first → skill body → `write-eval` for eval.yaml → behavioral test.
+### Phase 2: `write-docs`
+
+Build `write-docs` — the first skill authored via `write-skill` itself (the factory eating itself for the first time). Implement immediately after phase 1 is complete and deployed.
+
+**Trigger description** (from skills index): "Write documentation for X, document this module, create docs for this feature"
+
+**Key constraints:**
+- Skill file: `.agents/skills/write-docs/SKILL.md`; `metadata.category: implement`
+- SKILL.md authored via `write-skill`; eval via `write-eval`
+- Follow full per-skill workflow from `docs/notes/skill-implementation-workflow.md` (sub-agents for discovery, review, conflict check)
+- Derives from code and spec; never invents behaviour
 
 ## Implementation notes
 
@@ -36,7 +48,14 @@ Follow the per-skill workflow defined in `docs/notes/skill-implementation-workfl
 - [ ] `install.sh` deploys `write-skill` to `~/.agents/skills/`
 - [ ] **HITL:** human runs behavioral test: invoke "write a new skill for X" and verify the produced SKILL.md meets the authoring standard
 - [ ] **HITL:** human reviews SKILL.md and eval before committing
-- [ ] _(Further criteria to be refined after issue 0016 grill session)_
+- [ ] Per-skill process followed for both phases (see `docs/notes/skill-implementation-workflow.md`)
+- [ ] Trigger description for each skill tested against explicit, implicit, and negative queries before body written
+- [ ] `when:` frontmatter field present in both SKILL.md files
+- [ ] `source:` and `references:` fields correctly populated or absent
+- [ ] eval.yaml for each skill contains all 5 required test types
+- [ ] Body ≤500 lines for each skill
+- [ ] Phase 2 (`write-docs`) is the first skill produced end-to-end by the factory
+- [ ] `docs/spec/overview.md` updated to reflect both skills deployed
 
 ## Blocked by