Implement REUSE-WP-0012 federation scale and intent alignment

Add hub sync and report cohorts CLI commands with pytest coverage, document
sibling index publish contract and hub hardening path, align INTENT layout,
raise external evidence on three registry entries, and close gap priorities
19-23 (priority 18 deferred on sibling index blocks).

registry/README.md

@@ -143,6 +143,34 @@ Outputs:
 - `docs/graph/capability-graph.mmd` — Mermaid source
 - `docs/graph/index.html` — in-browser explorer (also regenerated by `catalog`)
 
+## External evidence checklist (R1 → R3)
+
+Use this when promoting **reliability** from **R1 Fragile** or **R2 Tolerable**
+to **R3 Usable** (normal use with known limitations).
+
+### Minimum evidence for R3
+
+- [ ] At least one **repeatable** quality signal (CI gate, smoke test, or
+  documented production check) cited under `evidence.tests` or `evidence.documentation`
+- [ ] `known_reliability_risks` lists bounded, current limitations (not empty
+  unless risks are genuinely absent)
+- [ ] At least one `evidence.consumer_feedback` string or resolved-risk note when
+  real consumers exist; otherwise document why feedback is not yet available
+- [ ] Optional `external_evidence.reliability.evidence.satisfied_signals` for CI
+  or smoke-test citations
+- [ ] `confidence` is `medium` or `high` when citing CI/production evidence
+- [ ] `promotion_history` records the R dimension change with rationale
+
+### Signals that support R3 for registry tooling
+
+- `reuse-surface validate` in CI with `--fail-on-warnings`
+- `pytest` coverage for the capability's consumption path
+- Production hub smoke (`GET /health`, `GET /v1/federated`) for API-backed flows
+- Operator deploy verification documented in `docs/deploy/reuse-kubernetes.md`
+
+R4+ requires broader consumer evidence (incidents, adoption, SLO) per
+`specs/CapabilityMaturityStandard.md`.
+
 ## Promote a capability
 
 1. Attach evidence appropriate to the target level in