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>

CHANGELOG.md

@@ -7,6 +7,30 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+#### Web Search Migration to Librarian
+- **`search_web()`** tool in Librarian for web search via library-desk `/rag/search` endpoint
+- **`read_url()`** tool for single URL content extraction via Trafilatura
+- **`read_urls_batch()`** tool for parallel batch URL extraction (max 20 URLs)
+- `WebSearchResult`, `WebSearchResponse` models in LibraryDeskClient
+- `ContentExtractionResult`, `BatchExtractionResponse` models for content extraction
+- `search_web()`, `extract_content()`, `extract_content_batch()` methods in LibraryDeskClient
+- Comprehensive unit tests for new Librarian tools (`tests/agents/librarian/test_tools.py`)
+
+### Changed
+
+- Librarian capability updated with web search domains: "web", "url", "internet"
+- Tatlock system prompt now delegates web search to Librarian
+- `tatlock_core` capability reduced to computation/datetime only (no longer requires network)
+
+### Removed
+
+- `search_web` function from `src/agents/tatlock_core/tools.py`
+- `web_search_tool` from `tatlock_core_tools` list
+- `search_web` from legacy `src/agents/tools.py`
+- Search tests from `tests/agents/test_tools.py` (moved to Librarian tests)
+
 ## [1.6.0] - 2025-12-15
 
 ### Added