fix(FN-2510): harden skills catalog fallback for short and invalid queries

- Update skills adapter fallback logic to handle empty and short catalog queries without surfacing 400 failures
- Handle ApiRequestError paths in SkillsView so invalid-query responses degrade gracefully in the UI
- Add regression coverage for adapter, routes, and SkillsView behavior across empty/short query cases
- Document short-query catalog behavior in the dashboard guide and include a patch changeset for @runfusion/fusion

docs/dashboard-guide.md

@@ -314,9 +314,14 @@ Fetch the skills.sh catalog with optional authentication.
 
 **Authentication Flow:**
 1. If `SKILLS_SH_TOKEN` env var is present, use authenticated request
-2. If authenticated request returns `401/403`, retry without authentication (fallback mode)
+2. If authenticated request returns `400/401/403`, retry without authentication (fallback mode)
 3. If no token, use unauthenticated request directly
 
+**Unauthenticated Short-Query Behavior:**
+- Public `skills.sh /api/search` requests are only sent when `q` has at least 2 characters
+- For omitted, empty, or 1-character queries, the API returns `200` with `{ entries: [] }`
+- This applies both to direct unauthenticated mode and authenticated-to-unauthenticated fallback mode, preventing upstream `400 Bad Request` responses during initial load
+
 **Auth Mode Values:**
 - `authenticated` — Request made with token
 - `unauthenticated` — Request made without token (no token available)