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.

scripts/type-equiv.manifest.json

@@ -1060,6 +1060,11 @@
       "symbol": "SkillLookupOptions",
       "source": "packages/skill/skill/src/index.ts"
     },
+    {
+      "doc": "docs/subsystems/skills.md",
+      "symbol": "SkillViewOptions",
+      "source": "packages/skill/skill/src/index.ts"
+    },
     {
       "doc": "docs/subsystems/skills.md",
       "symbol": "SkillProviderObservation",