feat: migrate web search from tatlock_core to Librarian

Move web search functionality to The Librarian agent, integrating with
the library-desk /rag/search endpoint for enhanced search capabilities.

Changes:
- Add search_web, read_url, read_urls_batch tools to Librarian
- Add WebSearchResult, ContentExtractionResult models to client
- Add search_web, extract_content, extract_content_batch client methods
- Update Librarian capability with web/url/internet domains
- Remove search_web from tatlock_core tools and toolset
- Update Tatlock system prompt to delegate web search to Librarian
- Add comprehensive unit tests for new Librarian tools
- Clean up legacy src/agents/tools.py

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/tatlock_core/capability.py

@@ -11,10 +11,10 @@ TATLOCK_CORE_CAPABILITY = HouseholdCapability(
     name="tatlock_core",
     role="Butler's Core Tools",
     category="core",
-    description="Essential tools for computation, date/time operations, and web searches",
-    domains=["computation", "datetime", "information", "research"],
+    description="Essential tools for computation and date/time operations",
+    domains=["computation", "datetime", "math", "calculator"],
     cost="low",
-    requires_network=True,  # For web search
+    requires_network=False,  # Web search moved to Librarian
 )