feat: Add empty query support to llm_search for listing all artifacts

Changes:
- fts_search_llm(): Empty query now returns all artifacts (list mode)
- Update llm.search tool: query parameter is now optional
- Tool description mentions empty query lists all artifacts
- Add body field to llm_search results
- Update demo script: Add special case for "What questions can I ask?"

This enables agents to retrieve all pre-defined question templates
when users ask what questions are available, instead of inferring
questions from schema.

lib/Discovery_Schema.cpp

@@ -1917,8 +1917,14 @@ std::string Discovery_Schema::fts_search_llm(
 	SQLite3_result* resultset = NULL;
 
 	std::ostringstream sql;
-	sql << "SELECT kind, key, title ,  bm25(fts_llm) AS score FROM fts_llm "
-	    << "WHERE fts_llm MATCH '" << query << "' ORDER BY score LIMIT " << limit << ";";
+	// Empty query returns all results (list mode), otherwise search
+	if (query.empty()) {
+		sql << "SELECT kind, key, title, body ,  0.0 AS score FROM fts_llm "
+		    << "ORDER BY kind, title LIMIT " << limit << ";";
+	} else {
+		sql << "SELECT kind, key, title, body ,  bm25(fts_llm) AS score FROM fts_llm "
+		    << "WHERE fts_llm MATCH '" << query << "' ORDER BY score LIMIT " << limit << ";";
+	}
 
 	db->execute_statement(sql.str().c_str(), &error, &cols, &affected, &resultset);
 
@@ -1932,7 +1938,8 @@ std::string Discovery_Schema::fts_search_llm(
 			item["kind"] = std::string(row->fields[0] ? row->fields[0] : "");
 			item["key"] = std::string(row->fields[1] ? row->fields[1] : "");
 			item["title"] = std::string(row->fields[2] ? row->fields[2] : "");
-			item["score"] = atof(row->fields[3] ? row->fields[3] : "0");
+			item["body"] = std::string(row->fields[3] ? row->fields[3] : "");
+			item["score"] = atof(row->fields[4] ? row->fields[4] : "0");
 
 			results.push_back(item);
 		}

lib/Query_Tool_Handler.cpp

@@ -643,9 +643,9 @@ json Query_Tool_Handler::get_tool_list() {
 
 	tools.push_back(create_tool_schema(
 		"llm.search",
-		"Full-text search across LLM artifacts (summaries/domains/metrics/templates/notes) using fts_llm.",
-		{"run_id", "query"},
-		{{"limit", "integer"}}
+		"Full-text search across LLM artifacts (summaries/domains/metrics/templates/notes) using fts_llm. Use empty query string to list all artifacts.",
+		{"run_id"},
+		{{"query", "string"}, {"limit", "integer"}}
 	));
 
 	// ============================================================
@@ -1408,8 +1408,6 @@ json Query_Tool_Handler::execute_tool(const std::string& tool_name, const json&
 
 		if (run_id_or_schema.empty()) {
 			result = create_error_response("run_id is required");
-		} else if (query.empty()) {
-			result = create_error_response("query is required");
 		} else {
 			// Resolve schema name to run_id if needed
 			int run_id = catalog->resolve_run_id(run_id_or_schema);

scripts/mcp/demo_agent_claude.sh

@@ -88,6 +88,38 @@ Here are the results:
 - **If no good match**: Generate SQL from scratch using catalog schema
 - **run_id**: Always use '${SCHEMA}' as the run_id
 
+## Special Case: "What questions can I ask?"
+
+When the user asks:
+- "What questions can I ask?"
+- "What are some example questions?"
+- "Show me available questions"
+
+**DO NOT** infer questions from schema. Instead:
+1. Call `llm_search` with `query=""` (empty string) to list all existing question templates
+2. Present the question templates grouped by type (question_template, metric, etc.)
+3. Show the title and body (the actual question) for each
+
+Example:
+```
+User: "What questions can I ask?"
+
+Step 1: List all available question templates...
+[Call llm_search with query=""]
+
+Step 2: Found X pre-defined questions:
+
+📊 Question Templates:
+- "What is the total revenue?"
+- "Who are the top customers?"
+...
+
+📈 Metrics:
+- "Revenue by Country"
+- "Monthly Revenue Trend"
+...
+```
+
 ## Example Interaction
 
 User: \"What are the most expensive tracks?\"