feat: parallel tool execution with automatic mutation serialization

- Add lightweight async mutex (src/util/mutex.ts) for FIFO serialization
- Add serialized?: boolean to BrowserToolDefinition
- Wire mutex acquisition into registerBrowserTool execute wrapper
- Expose mutationMutex() on BrowserClient
- Mark all mutation tools (click, type, scroll, navigate, switch_tab, etc.) as serialized
- Leave observation tools (screenshot, page_info, execute_js, http_get, etc.) unguarded
- Update prompt and skill docs to reflect parallel-safe behavior
- Fix scroll tool: add Page.bringToFront, explicit button:none/buttons:0/pointerType:mouse
- Update .gitignore to ignore scripts/ and data/ folders

1 files changed, 22 insertions, 19 deletions

diff --git a/src/registry.ts b/src/registry.ts
index 5f9d7da..d9b7cea 100644
--- a/src/registry.ts
+++ b/src/registry.ts
@@ -16,31 +16,34 @@ import { dragAndDropTool } from "./domains/drag";
 import { httpGetTool, getNetworkLogTool } from "./domains/network";
 import { executeJsTool, runScriptTool } from "./domains/js";
 
+// Mutation tools that modify page / browser state are marked `serialized: true`
+// so they run through a shared async mutex.  Observation / read-only tools are
+// left unmarked and can execute in parallel.
 const TOOLS: ReadonlyArray<AnyBrowserToolDefinition> = [
-  clickTool,
-  typeTool,
-  pressKeyTool,
-  dispatchKeyTool,
-  scrollTool,
+  { ...clickTool, serialized: true },
+  { ...typeTool, serialized: true },
+  { ...pressKeyTool, serialized: true },
+  { ...dispatchKeyTool, serialized: true },
+  { ...scrollTool, serialized: true },
   pageInfoTool,
   waitTool,
-  waitForLoadTool,
-  handleDialogTool,
+  { ...waitForLoadTool, serialized: true },
+  { ...handleDialogTool, serialized: true },
   screenshotTool,
-  navigateTool,
-  openUrlsTool,
-  goBackTool,
-  goForwardTool,
-  reloadTool,
+  { ...navigateTool, serialized: true },
+  { ...openUrlsTool, serialized: true },
+  { ...goBackTool, serialized: true },
+  { ...goForwardTool, serialized: true },
+  { ...reloadTool, serialized: true },
   listTabsTool,
   currentTabTool,
-  switchTabTool,
-  newTabTool,
-  uploadFileTool,
-  downloadTool,
-  printToPdfTool,
-  viewportResizeTool,
-  dragAndDropTool,
+  { ...switchTabTool, serialized: true },
+  { ...newTabTool, serialized: true },
+  { ...uploadFileTool, serialized: true },
+  { ...downloadTool, serialized: true },
+  { ...printToPdfTool, serialized: true },
+  { ...viewportResizeTool, serialized: true },
+  { ...dragAndDropTool, serialized: true },
   httpGetTool,
   getNetworkLogTool,
   executeJsTool,