feat(shared): add case-insensitive utilities for agent name matching

Add findCaseInsensitive, includesCaseInsensitive, findByNameCaseInsensitive,
and equalsIgnoreCase functions for consistent case-insensitive lookups across
the codebase. Enables 'Oracle', 'oracle', 'ORACLE' to work interchangeably.

src/shared/index.ts

@@ -29,3 +29,4 @@ export * from "./agent-tool-restrictions"
 export * from "./model-requirements"
 export * from "./model-resolver"
 export * from "./model-availability"
+export * from "./case-insensitive"