docs(skill): document the layered registry and record the Agent Note

The skills subsystem page and dsh-skill README describe the host+per-scope
layers, SkillViewOptions joins the type-equiv corpus and the cordis-catalog
type pages, generated catalogs pick up the shifted source refs, and the
architecture Agent Note records the decision, the nearest-layer-wins
precedence choice, and the rejected alternatives.

packages/skill/skill/README.md

@@ -6,15 +6,17 @@ Pure agent skill provider registry.
 
 This package owns the `ctx.skills` interface. It does not know whether skills come from local files, embedded plugin data, HTTP, or another backend; providers register those sources with `ctx.skills.registerProvider(...)`. The shipped local implementation is [`@deepseek-ai/dsh-skill-local`](../skill-local).
 
+The registry is host+per-scope layered over [`@deepseek-ai/dsh-scope`](../../core/scope), the shape the tools registry established: a registration files into the layer of its calling context's scope — host rows and repository plugins land in the global layer, a plugin mounted by an agent preset's standing composition lands in that preset's layer — and a read merges the global layer with the viewing scope's chain, the nearest layer winning a duplicate name outright while rank decides duplicates only within one layer.
+
 ## Service: `SkillService` (ctx key: `skills`)
 
 ### Public API
 
-- `ctx.skills.registerProvider(create): () => void` Calls a synchronous provider factory with `{ signal, invalidate }`, then registers its readonly result by unique `provider.name`. Duplicate names throw, `runtime` is reserved, and failed registration aborts the signal. The exact Cordis disposer unregisters the provider, aborts the signal, and preserves ordered composite teardown.
-- `ctx.skills.snapshot({ cwd?, signal? })` Returns the invocation-neutral `{ skills, complete }` observation. `complete` is false when any provider rejects or explicitly reports incomplete discovery, or when a second catalog revision races the bounded retry; candidates supplied by that observation remain in this result, which is never cached.
-- `ctx.skills.list({ cwd?, signal? })` Borrows the readonly lookup options, then returns every winning summary for the current workspace, merged across providers and sorted by name. Consumers apply `isModelInvocable(skill)` or `isUserInvocable(skill)` at their own boundary.
-- `ctx.skills.get(name, { cwd?, signal? })` Uses the same readonly options and winning candidate for discovery and loading, rechecks cancellation after discovery or a cache hit, races provider loading against the signal, validates the loaded definition, then returns it regardless of invocation policy.
-- `ctx.skills.register(skill): () => void` Registers a readonly runtime embedded skill, adding the all-invocable policy and `provider: "runtime"` when omitted. Same-name runtime registrations are first-wins: a duplicate logs a warning and gets a no-op disposer. Successful registrations return the exact Cordis disposer for ordered composite teardown.
+- `ctx.skills.registerProvider(create): () => void` Calls a synchronous provider factory with `{ signal, invalidate }`, then registers its readonly result by `provider.name`, unique within the calling context's layer. Duplicate names in one layer throw, `runtime` is reserved, and failed registration aborts the signal. The exact Cordis disposer unregisters the provider, aborts the signal, and preserves ordered composite teardown.
+- `ctx.skills.snapshot({ cwd?, signal?, scope? })` Returns the invocation-neutral `{ skills, complete }` observation for the viewing scope's merged layers. `complete` is false when any provider rejects or explicitly reports incomplete discovery, or when a second catalog revision races the bounded retry; candidates supplied by that observation remain in this result, which is never cached.
+- `ctx.skills.list({ cwd?, signal?, scope? })` Borrows the readonly view options, then returns every winning summary for the current workspace, merged across the global layer and the viewing scope's chain and sorted by name. Consumers apply `isModelInvocable(skill)` or `isUserInvocable(skill)` at their own boundary.
+- `ctx.skills.get(name, { cwd?, signal?, scope? })` Uses the same readonly options and winning candidate for discovery and loading, rechecks cancellation after discovery or a cache hit, races provider loading against the signal, validates the loaded definition, then returns it regardless of invocation policy.
+- `ctx.skills.register(skill): () => void` Registers a readonly runtime embedded skill into the calling context's layer, adding the all-invocable policy and `provider: "runtime"` when omitted. Same-name runtime registrations in one layer are first-wins: a duplicate logs a warning and gets a no-op disposer. Successful registrations return the exact Cordis disposer for ordered composite teardown.
 
 ### Events
 
@@ -49,7 +51,7 @@ A provider factory runs synchronously and receives one registration-scoped contr
 
 The registry validates candidates before caching and definitions before returning them. The winning provider receives the same candidate and opaque `locator` it returned from `list()`, allowing backend-specific file, URL, id, or version handles. Callers and providers must preserve the readonly contract.
 
-Contract violations fail fast. A rejected provider `list()` is treated as a transient source failure and omitted. An explicit incomplete observation still contributes its candidates for `list()` and `get()`, but makes the aggregate snapshot incomplete and uncacheable. A provider or runtime revision change discards an in-flight result and retries once. If the retry is also superseded, its candidates are returned incomplete and uncached so a continuously invalidating provider cannot monopolize the caller. Duplicate names resolve by rank, provider registration order, then provider-local order. Summaries are sorted by skill name.
+Contract violations fail fast. A rejected provider `list()` is treated as a transient source failure and omitted. An explicit incomplete observation still contributes its candidates for `list()` and `get()`, but makes the aggregate snapshot incomplete and uncacheable. A provider or runtime revision change discards an in-flight result and retries once. If the retry is also superseded, its candidates are returned incomplete and uncached so a continuously invalidating provider cannot monopolize the caller. Within one layer, duplicate names resolve by rank, provider registration order, then provider-local order; across layers the nearest scope's entry wins the name. Summaries are sorted by skill name.
 
 Definitions remain progressively loaded. `get()` asks the winning provider for the body on every call rather than caching it in this registry. If the returned definition has a different name from the selected candidate, the stale selection is rejected and the registry internally invalidates that exact provider so the next snapshot rediscovers its catalog.
 
@@ -74,4 +76,4 @@ No direct prompt effect. The named consumer owns the durable initial catalog and
 - **Invalidation is provider-driven** — the registry has no TTL and cannot infer that an arbitrary remote source changed; each mutable provider must retain and call its registration-scoped `invalidate()` capability from its own observation mechanism.
 - **Providers are queried sequentially** — one slow cooperative provider delays every provider registered after it; cancellation stops the caller's wait but cannot terminate work an uncooperative provider keeps running.
 - **Incomplete observations are not retained** — rejected providers are omitted and explicitly supplied candidates remain available only to the current lookup; the registry owns neither a last-good catalog nor per-provider diagnostics.
-- **Duplicate resolution is first-wins** — later lower-priority candidates are logged and hidden; there is no API to inspect all shadowed definitions.
+- **Duplicate resolution is first-wins** — later lower-priority candidates within a layer are logged and hidden, and a nearer layer shadows a farther one silently; there is no API to inspect all shadowed definitions.