feat(mcp): extend the server catalog to resources, templates, and prompts

Implements the unified catalog from plans/mcp-resources-prompts-design.md §4.2 (T2): CatalogItem gains kind/uri/mime_type/size keyed as {kind}:{id}; catalog_items() lists per kind gated by advertised capabilities with warn-and-degrade; mcp_search results carry kind; mcp_describe gains an optional kind param (default tool); write-only registry ServerCatalog removed.

src/config/mod.rs

@@ -51,6 +51,8 @@ pub use self::skill::Skill;
 pub use self::skill_policy::SkillPolicy;
 #[allow(unused_imports)]
 pub use self::skill_registry::SkillRegistry;
+#[cfg(test)]
+pub(crate) use self::tool_scope::test_fixtures;
 pub use self::update::run_self_update;
 use crate::client::{
     self, ClientConfig, MessageContentToolCalls, Model, ModelType, OPENAI_COMPATIBLE_PROVIDERS,