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>

LESSONS.md

@@ -10,6 +10,18 @@ Patterns observed during development of this repo. Three or more entries on the
 
 ---
 
+## 2026-05-17 — Workflow documents should prescribe sub-agent usage, not just allow it
+
+When writing workflow documents (like `docs/notes/skill-implementation-workflow.md`), the natural tendency is to describe steps at a high level and leave sub-agent usage as an implementation detail. But if the workflow doesn't explicitly prescribe "spawn a sub-agent here," practitioners default to doing everything in the main context — accumulating token cost and losing the isolation benefit. Fix: make sub-agent usage a named step in the workflow, specifying what the agent receives, what it returns, and why it's isolated. This makes the workflow reproducible rather than dependent on the practitioner remembering to use agents.
+
+## 2026-05-17 — Conflict check before synthesis grill, not during
+
+When combining upstream sources into a skill, conflicts with governing documents (AI constitution, factory principles) tend to surface in the middle of the synthesis grill — disrupting the combining discussion and requiring context switches. Fix: run a dedicated conflict-check step before the grill. A sub-agent reads the governing documents, checks the upstream content against them, and returns a numbered list of tensions. The grill then starts with those items as explicit agenda points, making it faster and more systematic. An empty conflict list is also valuable — it confirms the upstreams are clean before co-writing begins.
+
+## 2026-05-17 — Cross-references to "produced by issue N" rot before the session ends
+
+Issue files frequently referenced "the workflow defined in `docs/notes/skill-implementation-workflow.md` (produced by issue 0016)." Within the same session that closes issue 0016, that parenthetical is already stale — the document exists and is the authoritative reference. Fix: reference the document path directly, not the issue that produced it. The git history records the producing issue; cross-references should point to the artifact that persists.
+
 ## 2026-05-17 — "Read at session start" is a behavioral hope, not a guarantee
 
 The repo CLAUDE.md instructs agents to read CONTEXT.md and ROADMAP.md at session start, but agents skip this in practice — defaulting to reading only what's directly relevant to the immediate prompt (e.g. the skills folder). The governance.md works because `@import` is technically enforced by Claude Code. Fix: (1) add `@CONTEXT.md` to repo CLAUDE.md using `@import` to make it always-loaded; (2) add a "Key decisions" section to CONTEXT.md with one-line resolved-ADR summaries so locked choices are always in context. ROADMAP stays on-demand.