spec: extract use cases from wiki-engines landscape research (UC-34–UC-37)

Mine the one research dir not yet promoted (260608-wikiengines-overview) into
the catalog. Adds four heterogeneous-backend attachment scenarios the other
research didn't surface:

- UC-34 attach structured/semantic shard without lossy flattening (SMW, XWiki)
- UC-35 attach shard with coarse write granularity (TiddlyWiki single-file)
- UC-36 supply git-addressable history to internal-history engine (Confluence)
- UC-37 attach static export as read-only backup shard (MediaWiki dump)

Adds a `wikiengines` source token + traceability column and a wikiengines
mapping subsection. The scan mostly reinforced existing UCs and the L0→L4
ladder; its main yield is adapter-contract constraints tracked in SHARD-WP-0002.

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

spec/UseCaseCatalog.md

@@ -1,9 +1,10 @@
 # UseCaseCatalog
 
-Status: **draft** · Date: 2026-06-08 · Updated: 2026-06-08
+Status: **draft** · Date: 2026-06-08 · Updated: 2026-06-13
 
 Promoted from `research/260608-c2-wiki-origins/`,
-`research/260608-yawex-prior-art/`, and `research/260608-federation-concepts/`.
+`research/260608-yawex-prior-art/`, `research/260608-federation-concepts/`, and
+`research/260608-wikiengines-overview/`.
 See InfoTechPrimers on coulomb.social for use-case catalog conventions.
 
 ## Conventions
@@ -12,7 +13,7 @@ Each use case lists:
 
 - **Actor** — who initiates the action
 - **Goal** — observable outcome
-- **Source** — research lineage (`c2`, `yawex`, `federation`, `intent`, or combined)
+- **Source** — research lineage (`c2`, `yawex`, `federation`, `wikiengines`, `intent`, or combined)
 - **Notes** — shard-wiki-specific constraints or open design points
 
 Priority hints: **MVP** = likely early value; **Later** = important but not first slice.
@@ -175,6 +176,58 @@ divergent information space without destroying the original.
 Space-level fork — distinct from UC-26 page-level fork.  
 **Priority:** Later
 
+### UC-34 — Attach a structured or semantic shard without lossy flattening
+
+**Actor:** Maintainer  
+**Goal:** Attach an engine whose pages carry structured or queryable data beyond
+Markdown (Semantic MediaWiki annotations, XWiki objects/forms) and project it
+without silently discarding the structure.  
+**Source:** wikiengines, intent  
+**Notes:** Engine scan shows "wiki page" spans flat Markdown to queryable
+knowledge objects. Markdown-first must **degrade gracefully**, not flatten:
+needs a passthrough / sidecar-metadata / provenance escape hatch. Page-model
+question deferred to `SHARD-WP-0002` (findings §6 Q1). Distinct from UC-02
+(assumes Markdown-shaped pages).  
+**Priority:** Later
+
+### UC-35 — Attach a shard with coarse write granularity
+
+**Actor:** Maintainer  
+**Goal:** Attach a backend whose unit of write is not the page — a single-file
+wiki (TiddlyWiki) or a whole-space/DB-transaction engine — and have shard-wiki
+respect that granularity instead of assuming per-page writes.  
+**Source:** wikiengines, intent  
+**Notes:** Capability-aware adapters: the **capability profile must encode write
+granularity** (per-page / per-file / per-space / append-only). Overlay and
+patch flows must adapt (findings §5 #1). Affects conflict scope and locking.  
+**Priority:** Later
+
+### UC-36 — Supply a git-addressable history to an internal-history engine
+
+**Actor:** Maintainer  
+**Goal:** Attach an engine whose revisions live only in its own database
+(Confluence, MediaWiki) and give the information space a portable, git-backed
+history it otherwise lacks.  
+**Source:** wikiengines, intent  
+**Notes:** Many engines expose revisions but not portable, git-style history.
+The **coordination journal** supplies the Git-addressable layer (INTENT). Open:
+is the journal authoritative or a mirror reconciled back to the engine
+(findings §6 Q3)? Complements UC-07 divergence and UC-24 provenance.  
+**Priority:** Later
+
+### UC-37 — Attach a static engine export as a read-only backup shard
+
+**Actor:** Maintainer  
+**Goal:** Attach a one-shot export with no live origin — a MediaWiki XML dump, an
+HTML mirror, or an archived/read-only C2 — as a read-only cache/backup/patch
+target.  
+**Source:** wikiengines, intent  
+**Notes:** Graceful degradation — a frozen export is still a legitimate
+participant. Distinct from UC-03 (live projection with a reachable origin) and
+UC-28 (carry pages *forward* into a new space); here the dump itself is the
+shard. Read-only mode in `spec/ArchitectureBlueprint.md`.  
+**Priority:** Later
+
 ---
 
 ## B. Knowledge work and collaboration
@@ -370,23 +423,27 @@ CamelCase and `[[free links]]`. Markdown-first link semantics TBD.
 
 ## Traceability
 
-| UC | c2 research | yawex research | federation research | INTENT |
+| UC | c2 research | yawex research | federation research | wikiengines research | INTENT |
-|----|-------------|----------------|---------------------|--------|
+|----|-------------|----------------|---------------------|----------------------|--------|
-| UC-01 | ✓ | | | ✓ |
+| UC-01 | ✓ | | | | ✓ |
-| UC-02 | | ✓ | | ✓ |
+| UC-02 | | ✓ | | | ✓ |
-| UC-03 | | ✓ | ✓ | ✓ |
+| UC-03 | | ✓ | ✓ | | ✓ |
-| UC-04 | ✓ | ✓ | ✓ | ✓ |
+| UC-04 | ✓ | ✓ | ✓ | | ✓ |
-| UC-05 | ✓ | ✓ | ✓ | ✓ |
+| UC-05 | ✓ | ✓ | ✓ | | ✓ |
-| UC-06 | | ✓ | | ✓ |
+| UC-06 | | ✓ | | | ✓ |
-| UC-07 | | | ✓ | ✓ |
+| UC-07 | | | ✓ | | ✓ |
-| UC-26 | | | ✓ | ✓ |
+| UC-26 | | | ✓ | | ✓ |
-| UC-27 | | | ✓ | ✓ |
+| UC-27 | | | ✓ | | ✓ |
-| UC-28 | | | ✓ | |
+| UC-28 | | | ✓ | | |
-| UC-29 | | | ✓ | ✓ |
+| UC-29 | | | ✓ | | ✓ |
-| UC-30 | | | ✓ | |
+| UC-30 | | | ✓ | | |
-| UC-31 | | | ✓ | ✓ |
+| UC-31 | | | ✓ | | ✓ |
-| UC-32 | | | ✓ | ✓ |
+| UC-32 | | | ✓ | | ✓ |
-| UC-33 | | | ✓ | ✓ |
+| UC-33 | | | ✓ | | ✓ |
+| UC-34 | | | | ✓ | ✓ |
+| UC-35 | | | | ✓ | ✓ |
+| UC-36 | | | | ✓ | ✓ |
+| UC-37 | | | | ✓ | ✓ |
 | UC-08 | ✓ | | |
 | UC-09 | ✓ | | |
 | UC-10 | ✓ | | |
@@ -448,6 +505,21 @@ CamelCase and `[[free links]]`. Markdown-first link semantics TBD.
 | UC-FED-07 Transclude remote span | UC-32 |
 | UC-FED-08 Git-branch information space | UC-33 |
 
+### wikiengines mapping
+
+| Engine-landscape finding | Catalog UC |
+|--------------------------|------------|
+| Structured/semantic engines (Semantic MediaWiki, XWiki) — pages as queryable objects | UC-34 |
+| Coarse write granularity (TiddlyWiki single-file; whole-space DB writes) | UC-35 |
+| Internal-only revision history (Confluence, MediaWiki) needs portable git history | UC-36 |
+| Static exports / read-only archives (MediaWiki XML dump, archived C2, HTML mirror) | UC-37 |
+
+Note: the scan mostly **reinforced** existing UCs and the L0→L4 ladder rather than
+adding scenarios — its primary yield is adapter-contract constraints
+(`research/260608-wikiengines-overview/findings.md` §3, §5), tracked in
+`workplans/SHARD-WP-0002-federation-architecture.md`. UC-34–UC-37 are the
+genuinely new attachment scenarios it surfaced.
+
 ---
 
 ## Open questions