feat(mcp): note CRUD tools (list/get/create/update/delete)

Five tools wrapping services/notes.py with is_task=False. Signatures
mirror the existing fable-mcp note tool contracts so Claude usage is
unchanged.

Key behavior the tests pin down:
  - list_notes repackages (rows, total) tuple into {notes, total}
  - tag=""/search_text="" are "no filter" sentinels
  - update_note ONLY sends non-default fields to the service (the
    main risk: a default empty string overwriting real data)
  - tags=[] is an explicit clear; tags=None is "leave unchanged"
  - project_id=0 on create => orphan; on update => leave unchanged
    (preserved limitation from existing fable-mcp)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/fabledassistant/mcp/tools/__init__.py

@@ -4,9 +4,10 @@ Each tool module exposes a `register(mcp)` function that attaches its tools
 to a FastMCP instance. `register_all(mcp)` is the single entry point called
 from `mcp.server.build_mcp_server`.
 """
-from fabledassistant.mcp.tools import search
+from fabledassistant.mcp.tools import notes, search
 
 
 def register_all(mcp) -> None:
     """Register every tool module's tools on the given FastMCP instance."""
     search.register(mcp)
+    notes.register(mcp)