feat: add get_version MCP tool returning version and build hash

Agents can now call get_version to see what server version and commit
they're running against.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/http/mcp/mod.rs

@@ -837,6 +837,14 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                         }
                     }
                 },
+                {
+                    "name": "get_version",
+                    "description": "Return the server version and build hash.",
+                    "inputSchema": {
+                        "type": "object",
+                        "properties": {}
+                    }
+                },
                 {
                     "name": "rebuild_and_restart",
                     "description": "Rebuild the server binary from source and re-exec with the new binary. Gracefully stops all running agents before restart. If the build fails, the server stays up and returns the build error.",
@@ -1266,6 +1274,7 @@ async fn handle_tools_call(
         "get_pipeline_status" => story_tools::tool_get_pipeline_status(ctx),
         // Diagnostics
         "get_server_logs" => diagnostics::tool_get_server_logs(&args),
+        "get_version" => diagnostics::tool_get_version(),
         // Server lifecycle
         "rebuild_and_restart" => diagnostics::tool_rebuild_and_restart(ctx).await,
         // Permission bridge (Claude Code → frontend dialog)
@@ -1423,7 +1432,8 @@ mod tests {
         assert!(names.contains(&"status"));
         assert!(names.contains(&"loc_file"));
         assert!(names.contains(&"dump_crdt"));
-        assert_eq!(tools.len(), 62);
+        assert!(names.contains(&"get_version"));
+        assert_eq!(tools.len(), 63);
     }
 
     #[test]