research: Wiki.js deep dive (storage-module engine, DB<->Git Markdown, GraphQL); UC-68/69

The closest existing engine to shard-wiki's own design: DB-canonical
(Postgres/MySQL/SQLite) but with a pluggable storage-module abstraction
that bidirectionally syncs clean Markdown (+ YAML frontmatter) to Git
(also FS/S3/Azure), each provider acting as backup or source of truth.
Two big findings: (1) the storage-module interface is concrete
adapter-contract prior art alongside Foswiki::Store, and the closer one
(medium = Markdown in Git); (2) the engine-maintained bidirectional Git
mirror is the ideal file-store attach (clean MD + git history) and, being
bidirectional, makes git commit a write path (overlay/patch as a commit,
no API). Also GraphQL API (introspection = capability discovery;
selective fields = efficient projection) and authn-delegated auth modules
+ path-based rule ACL. Added UC-68 (engine-maintained bidirectional Git
mirror, write-by-commit), UC-69 (typed/introspectable API for schema
discovery + selective projection); enriched UC-06/36/38/40/42/57. Catalog
now 69 UCs. Architecture for SHARD-WP-0002 T11/T14: storage-module
abstraction as 2nd adapter-contract prior art, engine-maintained Git
mirror as attach+write surface, GraphQL introspection for capability
discovery.

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

SCOPE.md

@@ -19,9 +19,9 @@ Learnings update both SCOPE and INTENT where necessary.
 |-------|-------|
 | Code | Python package scaffold (`src/shard_wiki/`, smoke tests only) |
 | Intent | `INTENT.md` established; authorization-in-core amendments drafted |
-| Research | yawex prior art; c2 origins; federation concepts; wikiengines overview (`research/260608-*/`); XWiki/TWiki/Foswiki deep dives (`research/260613-*/`); Xanadu + ZigZag + Roam + Obsidian + Notion + Joplin + Logseq + local-first workspaces (Anytype/AFFiNE/AppFlowy) + Trilium deep dives & shard-spectrum synthesis (`research/260614-*/`) |
+| Research | yawex prior art; c2 origins; federation concepts; wikiengines overview (`research/260608-*/`); XWiki/TWiki/Foswiki deep dives (`research/260613-*/`); Xanadu + ZigZag + Roam + Obsidian + Notion + Joplin + Logseq + local-first workspaces (Anytype/AFFiNE/AppFlowy) + Trilium + Wiki.js deep dives & shard-spectrum synthesis (`research/260614-*/`) |
 | Demand | NetKingdom integration asks captured, not yet negotiated |
-| Spec | Architecture blueprint drafted; UseCaseCatalog 67 UCs from research; PRD/TSD scaffolds |
+| Spec | Architecture blueprint drafted; UseCaseCatalog 69 UCs from research; PRD/TSD scaffolds |
 | Work | `SHARD-WP-0001` active (6 tasks); `SHARD-WP-0002` active (16 tasks: T1–T10 federation + T11–T16 adapter contract) |
 
 ## In Scope (today)