feat(cli): collections manifest + ls + journeys; rename to kv::shared_collection (§11.6 C5)

Finish the §11.6 KV slice: declarative authoring, read-only inspection, the
runtime journey, and docs — plus a forced SDK-name fix.

- SDK name: `shared` is a Rhai RESERVED keyword, so `kv::shared(...)` is a parse
  error. Renamed the handle constructor to `kv::shared_collection(...)`
  (keeps the user's "shared" intent; unambiguous). Updated everywhere.
- CLI manifest: `collections = [...]` on `[group]` only (ManifestApp has no such
  field + deny_unknown_fields → an app manifest carrying it is a hard error);
  Manifest::collections() accessor; build_bundle emits it.
- plan/apply: a `collection` row group in `pic plan`; created/deleted counts in
  the apply summary; collections threaded through PlanDto/NodePlanDto/
  ApplyReportDto.
- read-only `pic collections ls --group` → GET /admin/groups/{id}/collections
  (viewer+), backed by ApplyService::collection_report + CollectionInfo.
- journey: a group declares `catalog`; app A writes, app B (same subtree) reads
  it back; a sibling-subtree app gets CollectionNotShared; `collections ls` +
  re-apply NoOp. Full suite 114/114.
- docs: groups-and-project-tool §11.6 (KV-only MVP shipped + deferrals),
  sdk-shape.md (the shared-collection handle + trust model), CLAUDE.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/sdk-shape.md

@@ -74,6 +74,31 @@ collection, id)` for docs. Collections are **mandatory**, not optional
 — even single-collection apps name their collection. The service layer
 rejects requests with empty collection names.
 
+### Shared group collections (§11.6)
+
+`kv::collection(name)` is **app-private** — scoped to `cx.app_id`, the
+isolation boundary. A separate, explicit handle reaches a **group-shared**
+KV collection that every app in a group's subtree reads (and an
+authenticated editor+ writes):
+
+```rhai
+let cat = kv::shared_collection("catalog");   // resolves the nearest
+cat.set("sku-1", #{ price: 9 });               // ancestor group that
+let p = cat.get("sku-1");                       // declares "catalog"
+```
+
+The name is deliberately distinct from `kv::collection` — a script opts
+into shared scope explicitly (implicit shadowing would silently redirect a
+write across apps). (`kv::shared` would be ideal but `shared` is a Rhai
+reserved word, hence `shared_collection`.) The owning group is resolved
+from `cx.app_id`'s ancestor chain — that walk is the isolation boundary;
+an app outside the owning group's subtree gets a "not a shared collection"
+error, never another subtree's data. A collection is made shared
+declaratively (`[group]` manifest `collections = [...]`), never from a
+script. **Reads** are open to any subtree script (including anonymous
+public endpoints — declaring the collection *is* the grant); **writes**
+require an authenticated principal with editor+ on the owning group.
+
 ## Error convention
 
 - **Throw on failure.** `widgets.set("k", "v")` throws a Rhai runtime