Add /start ceremony dials (START_APPROVAL_GATE, ISSUE_FULL_STRUCTURE) for lighter-ceremony projects

[sebastientaggart]

Summary

Re-scopes #200 from "build a parallel github-lite skill group" to two runtime toggles on the existing group — closing the real ceremony gap without the permanent cost of duplicating ~10 skill files and a doubled level×adapter test matrix.

Since #200 was filed, Code Cannon grew the runtime dials its agent notes had rejected (REVIEW_GATE: advisory, trunk mode, optional QA/labels/milestones) and a three-tier setup UX (Lightweight/Standard/Governed). The Lightweight profile already delivered most of the ticket. The only ceremony left un-relaxed lived in /start — the human gates and the mandated issue documentation. Two truthiness toggles finish the job. (Full reasoning posted as a comment on #200.)

New dials

Both default to "true", so every existing project renders byte-for-byte identically — the full-ceremony workflow is unchanged.

• START_APPROVAL_GATE — "false" makes /start skip the Case A & Case B "type go" gates and proceed straight to coding.
• ISSUE_FULL_STRUCTURE — "false" makes /start write a brief freeform issue body and skip the "Agent Implementation Notes" comment.

The Lightweight setup profile now writes both as "false". Kept for Lightweight: tickets, feature branches, PRs — the professional-signal artifacts.

Changes

• skills/github-agile/start.md — both gates, the five-section body, and the agent-notes comment wrapped in {{#if}} with relaxed variants.
• config.schema.yaml, templates/codecannon.yaml, .codecannon.yaml — declared both placeholders (CC itself stays full-ceremony).
• skills/github-agile/setup.md — Lightweight profile writes both "false"; health summary reports them.
• Regenerated all four adapter outputs (.claude, .cursor, .agents, .gemini).

Test plan

• ./sync.py --validate and make check pass (placeholder, permission, command-shape).
• Full-ceremony render ("true"): behavior unchanged; no placeholder leaks. Only cosmetic delta is the Step 2 heading "HUMAN GATE" → "Approach checkpoint" (same prompt text and stop-and-wait).
• Relaxed render ("false"): flip-tested — lite body + no-gate variants render in Case A and Case B, full-only text absent, zero {{ leaks. Config reverted after.

Closes #200

[sebastientaggart]

Code review — medium effort

Scope: /start ceremony toggles (START_APPROVAL_GATE, ISSUE_FULL_STRUCTURE) + schema/template/setup wiring. Both render paths ("true" / "false") were rendered and inspected; no placeholder leaks, make check + --validate pass. No sensitive-area surfaces touched (auth / payments / secrets / prod config / destructive ops) — sensitive-area gate not triggered.

[WARNING] skills/github-agile/start.md:320 — Case B's no-gate variant says "Do not stop to wait for a go — proceed directly to Step 3", but Case B Step 3 (Investigation findings) is itself an agent-initiated post/skip prompt. So with START_APPROVAL_GATE: "false" a resumed issue can still stop, contradicting the schema's promise that the gate is skipped and /start "proceeds straight through to coding without stopping." Either fold the Step 3 findings prompt under START_APPROVAL_GATE (default to skip silently when off, as the story-driver already does), or narrow the schema/variant wording to say only the approval gate is removed. Non-blocking — the prompt only fires on a genuine finding.

[NOTE] skills/github-agile/start.md:121 — the Step 2 heading rename HUMAN GATE → Approach checkpoint also lands in the full-ceremony ("true") render. Behavior is identical (same prompt, same stop-and-wait), so the "full-ceremony unchanged" criterion holds in substance, but the heading text differs from what existing projects saw before.

Verdict: APPROVE

[sebastientaggart]

Code review (re-review after fix) — medium effort

Scope: follow-up commit c4f0357 addressing the prior [WARNING]. Case B Step 3's investigation-findings prompt is now wrapped in {{#if START_APPROVAL_GATE}}, with a {{#if !START_APPROVAL_GATE}} variant that skips silently (posting a genuine finding without asking, mirroring the story-driver). Conditional blocks balanced; both render paths ("true" / "false") rendered and inspected — no placeholder leaks, make check + --validate pass. No sensitive-area surfaces touched.

Prior warning resolved. No new findings.

Verdict: APPROVE