feat(phase3): register Librarian on application startup

- Add Librarian registration to household member registration
- Error handling to prevent startup failure if Librarian unavailable

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

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

src/core/startup.py

@@ -5,6 +5,7 @@ Handles initialization of household registry and other startup tasks.
 This module should be called during application startup to register
 all household members.
 """
+from src.agents.librarian import register_librarian
 from src.agents.tatlock_core import TATLOCK_CORE_CAPABILITY, tatlock_core_tools
 from src.core.household_registry import get_household_registry
 from src.core.logging_config import get_logger
@@ -21,11 +22,7 @@ def register_household_members():
 
     Currently registers:
     - tatlock_core: Butler's core tools (calculator, datetime, web search)
-
-    Future phases will add:
-    - librarian: Research and knowledge management
-    - developer: Software development assistance
-    - etc.
+    - librarian: Research and knowledge management (Phase 3)
     """
     registry = get_household_registry()
 
@@ -45,6 +42,16 @@ def register_household_members():
         tool_count=len(tatlock_core_tools),
     )
 
+    # Register The Librarian (Phase 3)
+    try:
+        register_librarian()
+    except Exception as e:
+        # Don't fail startup if Librarian registration fails
+        logger.warning(
+            "librarian_registration_failed",
+            error=str(e),
+        )
+
     logger.info(
         "household_registration_complete",
         total_members=len(registry),