docs(structure): add requirements contract, job namespaces, and enforcement gate

Phase 1 scaffold for the docs consolidation:

- docs/STRUCTURE.md: artifact registry, 8 owner-job ID namespaces, routing and change rules
- docs/REQUIREMENTS.md, docs/MILESTONES.md: normative schema, empty pending Phase 2 port
- docs/_templates/: requirement-row, capability, contract, adr
- docs/capabilities/, docs/contracts/: registered homes
- tools/check_requirements.py: enforces registry, IDs, and traceability
- AGENTS.md: coding paused banner + structure-contract routing rule
- README.md: pointers to the structure/requirements/milestones set

Additive only: no doc moves, no requirement text, no CI wiring yet.

docs/REQUIREMENTS.md

@@ -0,0 +1,58 @@
+# Requirements
+
+Normative source of truth. One row per requirement. Enforced by `tools/check_requirements.py`.
+
+A requirement is defined here and nowhere else. Capability and contract docs cite IDs; they do not restate them.
+
+Format and rules: `docs/STRUCTURE.md`.
+Scope: `shipped` | `M3` | `later`. `Test` is required for `shipped` and `M3`; use `—` for `later`.
+
+Populated in Phase 2 from the `pre-simplification` tag and the current docs.
+
+## CAPTURE — ecommerce-ready capture
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## METADATA — listing attributes and copy
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## REVIEW — confirm, tweak, ready
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## PUBLISH — store submission
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## SETTINGS — configured once
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## APP — device draft and state
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## OPS — deploy and release
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |
+
+## QUALITY — verification
+
+| ID | Requirement | Scope | Test |
+|---|---|---|---|
+| — | *(none yet)* | — | — |