docs: record Inception Sprint Oath; descope S3 (var-go enforcement) to #1

Add docs/INCEPTION-OATH.md — the sprint's acceptance contract (general +
cad-atlas-specific clauses, tagging as the closing act). S3 (var-go/oath
enforcing cad-atlas PRs) is descoped to a tracked fast-follow (#1): var-go v1's
candidate is a hardcoded self-test and its module is not cross-repo consumable,
so a green status would prove wiring, not verification. Honesty rule: a clause
blocked by an external dependency is descoped and tracked, never claimed.

Methodology persisted: brain wiki/homelab/decisions/inception-sprint-and-oath.md

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -340,6 +340,7 @@ is advisory here. Wiring it is a first tracked task; disclosed in code, this doc
 ## Brain references (source of truth — `brain_get <path>`)
 
 - `wiki/homelab/decisions/cad-atlas-audit-chain-is-viz-data.md` — **this project's genesis note**: the audit-chain-is-viz-data thesis, the three gates, template-go-web footguns
+- `wiki/homelab/decisions/inception-sprint-and-oath.md` — the Inception Sprint + Oath methodology (this repo's birth is the worked example); see [`docs/INCEPTION-OATH.md`](docs/INCEPTION-OATH.md) for the kept Oath
 - `knowledge/workflow-idea-to-running-service.md` — Double Diamond idea→service workflow
 - `wiki/homelab/decisions/continuous-agentic-development-cad-concept-2026-06-16.md` — CAD definition
 - `wiki/agentsquad/decisions/cad-dispatch-bridge.md` — claude.ai → agentsquad trigger path