feat(mcp): tools/ package + fable_search

Establishes the tool pattern: each tool module exposes register(mcp),
register_all() aggregates them, build_mcp_server() calls register_all.

fable_search mirrors the existing fable-mcp contract (q/content_type/limit
in; {results, total} out) but calls services.embeddings.semantic_search_notes
directly instead of going over HTTP. User comes from mcp.current_user_id().

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

src/fabledassistant/mcp/server.py

@@ -24,7 +24,8 @@ Hierarchy: Project -> Milestone -> Task/Note.
 def build_mcp_server() -> FastMCP:
     """Build the FastMCP instance with all tools registered."""
     mcp = FastMCP("fable", instructions=_INSTRUCTIONS.strip())
-    # Tools will be registered here in Phase 2/3.
+    from fabledassistant.mcp.tools import register_all
+    register_all(mcp)
     return mcp
 
 

src/fabledassistant/mcp/tools/__init__.py

@@ -0,0 +1,12 @@
+"""MCP tool implementations.
+
+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
+
+
+def register_all(mcp) -> None:
+    """Register every tool module's tools on the given FastMCP instance."""
+    search.register(mcp)

src/fabledassistant/mcp/tools/search.py

@@ -0,0 +1,49 @@
+"""fable_search — semantic search across the user's notes and tasks.
+
+Mirrors the existing fable-mcp contract so Claude's prior usage pattern keeps
+working. Differences from fable-mcp:
+  - calls services.embeddings.semantic_search_notes directly instead of HTTP
+  - user_id comes from mcp.current_user_id() rather than a global API key
+"""
+from __future__ import annotations
+
+from fabledassistant.mcp._context import current_user_id
+from fabledassistant.services.embeddings import semantic_search_notes
+
+
+async def fable_search(q: str, content_type: str = "all", limit: int = 10) -> dict:
+    """Semantic search over the user's notes and tasks.
+
+    Args:
+        q: search query string.
+        content_type: 'all' (default), 'note' (notes only), or 'task' (tasks only).
+        limit: maximum number of results (1-50).
+
+    Returns:
+        {"results": [{"id", "title", "body", "is_task", "tags", "similarity"}],
+         "total": int}
+    """
+    uid = current_user_id()
+    limit = max(1, min(limit, 50))
+    is_task = {"note": False, "task": True}.get(content_type)  # None => any
+    raw = await semantic_search_notes(
+        uid, q, limit=limit, is_task=is_task,
+    )
+    return {
+        "results": [
+            {
+                "id": note.id,
+                "title": note.title,
+                "body": (note.body or "")[:240],
+                "is_task": bool(note.is_task),
+                "tags": list(note.tags or []),
+                "similarity": float(score),
+            }
+            for score, note in raw
+        ],
+        "total": len(raw),
+    }
+
+
+def register(mcp) -> None:
+    mcp.tool(name="fable_search")(fable_search)