Add semantic search (RAG) for registry tool discovery

Users can now find tools by describing what they need in natural language.
Uses Ollama embeddings (nomic-embed-text) on AI-Server for vector similarity
search. Available via CLI (registry describe), GUI (AI search row), and API.

New files:
- registry/embeddings.py: core embedding logic (Ollama API, cosine similarity,
  pack/unpack vectors, backfill)
- tests/test_embeddings.py: 16 unit tests

Modified:
- registry/db.py: tool_embeddings table (schema + migration)
- registry/settings.py: embeddings.* settings (ollama_url, model, enabled, min_score)
- registry/app.py: semantic-search endpoint, publish hook, admin backfill/status
- registry_client.py: semantic_search() method with error surfacing
- gui/pages/registry_page.py: AI search row with SemanticSearchWorker
- cli/__init__.py + registry_commands.py: registry describe subcommand

Backfill required after deploy: POST /api/v1/admin/embeddings/backfill

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/cmdforge/cli/registry_commands.py

@@ -37,6 +37,8 @@ def cmd_registry(args):
         return _cmd_registry_status(args)
     elif args.registry_cmd == "browse":
         return _cmd_registry_browse(args)
+    elif args.registry_cmd == "describe":
+        return _cmd_registry_describe(args)
     elif args.registry_cmd == "config":
         return _cmd_registry_config(args)
     else:
@@ -53,6 +55,7 @@ def cmd_registry(args):
         print("  my-tools           List your published tools")
         print("  status <tool>      Check moderation status of a tool")
         print("  browse             Browse tools (GUI)")
+        print("  describe <query>   Find tools by describing what you need (AI)")
         print("  config [action]    Manage registry settings (admin)")
         return 0
 
@@ -894,6 +897,67 @@ def _cmd_registry_status(args):
     return 0
 
 
+def _cmd_registry_describe(args):
+    """Find tools by describing what you need (semantic search)."""
+    from ..registry_client import RegistryError, get_client
+
+    query = args.query
+    limit = getattr(args, 'limit', 20)
+
+    try:
+        client = get_client()
+        result = client.semantic_search(query, limit=limit)
+
+        # JSON output
+        if getattr(args, 'json', False):
+            print(json.dumps(result, indent=2))
+            return 0
+
+        available = result.get("available", False)
+        tools = result.get("data", [])
+        error = result.get("error")
+
+        if error:
+            print(f"Error: {error}", file=sys.stderr)
+            return 1
+
+        if not available:
+            print("AI search is not available on this registry.")
+            print("The Ollama embedding service may be offline or the feature is disabled.")
+            return 1
+
+        if not tools:
+            print(f'No tools found matching: "{query}"')
+            print("Try different phrasing or use keyword search: cmdforge registry search <query>")
+            return 0
+
+        print(f'Found {len(tools)} tools matching: "{query}"\n')
+
+        for i, tool in enumerate(tools, 1):
+            similarity = tool.get("similarity", 0)
+            pct = f"{similarity * 100:.0f}%"
+            owner = tool.get("owner", "")
+            name = tool.get("name", "")
+            desc = tool.get("description", "")
+
+            print(f"  {i}. {owner}/{name} ({pct} match)")
+            if desc:
+                print(f"     {desc[:70]}{'...' if len(desc) > 70 else ''}")
+            print()
+
+    except RegistryError as e:
+        if e.code == "CONNECTION_ERROR":
+            print("Could not connect to the registry.", file=sys.stderr)
+        else:
+            print(f"Error: {e.message}", file=sys.stderr)
+        return 1
+    except Exception as e:
+        print(f"Error: {e}", file=sys.stderr)
+        return 1
+
+    return 0
+
+
 def _cmd_registry_browse(args):
     """Browse tools (GUI)."""
     from ..gui import run_gui