Fix MCP & title bar (#1348)

<!-- This is an auto-generated description by cubic. -->

## Summary by cubic
Fixes MCP handoff by detecting an edit-code tool call and stopping
generation. Simplifies the title bar credit tooltip; also blocks dyad-*
tags in the system prompt and updates tests.

- **Bug Fixes**
- Stop generation on edit-code via hasToolCall; add a no-op edit-code
tool to signal handoff.
  - Combine tool-call stop with existing step limit for reliability.
  - Forbid <dyad-*> tags in the system prompt to prevent misuse.
- Remove credit usage/reset details from the title bar tooltip; keep the
delay note.
  - Update e2e snapshot to reflect the new prompt rule.

<!-- End of auto-generated description by cubic. -->

src/app/TitleBar.tsx

@@ -235,14 +235,6 @@ export function AICreditStatus({ userBudget }: { userBudget: UserBudgetInfo }) {
       </TooltipTrigger>
       <TooltipContent>
         <div>
-          <p>
-            You have used {Math.round(userBudget.usedCredits)} credits out of{" "}
-            {userBudget.totalCredits}.
-          </p>
-          <p>
-            Your budget resets on{" "}
-            {userBudget.budgetResetDate.toLocaleDateString()}
-          </p>
           <p>Note: there is a slight delay in updating the credit status.</p>
         </div>
       </TooltipContent>