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>

research/260614-wikijs-deep-dive/README.md

@@ -0,0 +1,49 @@
+# 260614 — Wiki.js deep dive (the storage-module engine that already speaks Git + Markdown)
+
+Date: 2026-06-14
+
+## What this is
+
+A focused study of **Wiki.js** — the modern Node.js server wiki — read through
+shard-wiki's lens. Wiki.js is the **closest existing engine to shard-wiki's own design**:
+it is DB-canonical (Postgres/MySQL/SQLite) **but abstracts persistence behind pluggable
+"storage modules"** — Git, local filesystem, S3, Azure Blob — each acting as **backup or
+source of truth**, with the **Git module bidirectionally syncing clean `.md` files (+ YAML
+frontmatter)** to a repo. That storage-module interface is, in effect, a shipped version
+of shard-wiki's adapter contract — the second concrete prior art after **Foswiki::Store**,
+and the closer one (medium = Markdown in Git).
+
+Distinctive material:
+- **Architecture** — Node.js/Vue; **GraphQL API** over all resources; DB-canonical;
+  Markdown (primary) + HTML + AsciiDoc; path-based hierarchy; modular
+  (storage/auth/search/render/editor)
+- **Storage modules** — provider connector (Git/FS/S3/Azure) with properties + create/
+  update/delete/sync methods, **backup-or-source-of-truth**, `injectMetadata()` YAML
+  frontmatter; **Git module commits every change → version-controlled clean Markdown**,
+  bidirectional
+- **GraphQL** — typed, **introspectable** (capability/schema discovery), **selective-field**
+  projection
+- **Auth modules** (delegated authn) + **path-based rule ACL**
+
+## Contents
+
+| Path | Role |
+|------|------|
+| `findings.md` | Architecture, storage modules (≈ adapter contract), Git mirror as attach+write surface, GraphQL, access control, capability profile, INTENT mapping, UC seeds, architecture notes, sources |
+
+## Status
+
+Initial deep dive complete. Two new use cases promoted to `spec/UseCaseCatalog.md` (UC-68
+attach an engine-maintained bidirectional Git mirror of clean Markdown, incl. write-by-
+commit; UC-69 attach via a typed, introspectable API — GraphQL — for schema discovery +
+selective projection); UC-06/36/38/40/42/57 enriched. Logged for `SHARD-WP-0002`
+(T11/T14): the **storage-module abstraction as a second adapter-contract prior art** (with
+Foswiki::Store), the **engine-maintained Git mirror** as preferred attach+write surface,
+and **GraphQL introspection** for capability discovery + selective projection.
+
+**Key takeaway recorded:** Wiki.js is the most shard-wiki-shaped engine yet — its
+storage-module interface is near-isomorphic to the adapter contract, and its
+Markdown-in-Git mirror is the ideal file-store attach (clean MD, git history,
+write-by-commit). **Boundary:** one server-engine candidate shard, DB-canonical with a
+maintained Git mirror; don't double-sync; honor its access rules; not the federation layer.
+</content>