Register shard-wiki capabilities (7 wiki.* registry entries)

Adds capability.wiki.{shard-orchestration, adapter-contract, page-model,
coordination-journal, overlay, federation-models, engine-typed-extensions}
with honest D/A/C/R maturity vectors, relations, and shard-wiki spec/test
evidence; updates registry/indexes/capabilities.yaml. reuse-surface validate: ok.
Source: shard-wiki SHARD-WP-0013 T1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

registry/capabilities/capability.wiki.page-model.md

@@ -0,0 +1,104 @@
+---
+id: capability.wiki.page-model
+name: Backend-Neutral Wiki Page Model
+summary: A Markdown-first but stretchable page model with stable identity separate from placement and layered provenance, spanning prose to typed-graph and computational shapes.
+owner: shard-wiki
+status: draft
+domain: helix_forge
+tags: [wiki, page-model, identity, provenance, markdown, shard-wiki]
+
+maturity:
+  discovery:
+    current: D5
+    target: D6
+    confidence: high
+    rationale: >
+      Page shapes (prose, typed records, typed-graph, inline-embedded, non-Markdown,
+      and four computational shapes) plus identity != placement and layered provenance
+      are specified and grounded in the dive research.
+  availability:
+    current: A2
+    target: A5
+    confidence: medium
+    rationale: >
+      Identity/Placement/Span/Page and layered ProvenanceEnvelope exist as a source
+      module; richer shapes (typed-graph, notebook) are modeled but not all built.
+
+external_evidence:
+  completeness:
+    level: C2
+    name: Partial
+    confidence: medium
+    basis: scope_vs_intent_and_consumer_expectations
+    satisfied_expectations:
+      - stable identity distinct from placement and from content fingerprint
+      - layered (effective-vs-own) provenance with near-zero per-span cost
+    broken_expectations:
+      - non-prose shapes (typed-graph, notebook, inline-embedded) not fully realized
+    out_of_scope_expectations:
+      - rendering / presentation
+  reliability:
+    level: R1
+    confidence: low
+    basis: consumer_quality_signals
+    known_reliability_risks:
+      - prose shape is the only exercised path so far
+
+discovery:
+  intent: >
+    One backend-neutral lingua franca every consumer sees; every shape reduces to
+    (content|source, structure, provenance envelope, optional derivation rule).
+  includes:
+    - page identity (stable handle) vs placement (N paths/shards) vs equivalence (fingerprint)
+    - layered provenance envelope (page + span deltas)
+    - page-shape taxonomy incl. computational shapes
+  excludes:
+    - deriving identity from content (a fingerprint identifies a version, not a page)
+  use_cases:
+    - "shard-wiki UseCaseCatalog UC-34, UC-39, UC-44..UC-49, UC-55, UC-73, UC-83, UC-84"
+
+availability:
+  current_level: A2
+  target_level: A5
+  current_artifacts:
+    - "shard-wiki/src/shard_wiki/model/"
+    - "shard-wiki/src/shard_wiki/provenance/"
+  consumption_modes:
+    - source module
+
+relations:
+  supports:
+    - capability.wiki.adapter-contract
+    - capability.wiki.shard-orchestration
+
+evidence:
+  documentation:
+    - "shard-wiki/spec/CoreArchitectureBlueprint.md (Section 7)"
+    - "shard-wiki/spec/FederationRequirements.md (ADR-02, ADR-04)"
+  tests:
+    - "shard-wiki/tests/test_model.py"
+    - "shard-wiki/tests/test_provenance.py"
+
+consumer_guidance:
+  recommended_for:
+    - a portable, provenance-carrying representation of wiki pages across backends
+  not_recommended_for:
+    - cases needing a single canonical path per page (use identity, not path)
+  known_limitations:
+    - non-prose shapes specified ahead of implementation
+---
+
+# Backend-Neutral Wiki Page Model
+
+The top narrow waist: a Markdown-first model that stretches to typed records, typed-graph
+statements, inline-embedded objects, non-Markdown assets, and computational shapes. Identity
+is a stable handle; placement and equivalence are separate mechanisms; provenance is layered
+(effective = page envelope + span delta).
+
+## Assessment notes
+
+### Discovery
+Specified in CoreArchitectureBlueprint Section 7 and FederationRequirements ADR-02/04.
+
+### Availability
+`model/` + `provenance/` ship the prose path and the layered envelope today.