fix(extension): keep user-opened tabs free & fix agent-tab leak on session stop (issue #57)

- session_stop: exclude tabs still tracked in agentCreatedTabs from the
  release decision so a tab that failed to close is no longer mistaken for
  a user tab (which previously kept the window open and leaked the tab).
- Distinguish user-created tabs from agent-created tabs in the Agent Window
  via a pending-tab counter consumed by chrome.tabs.onCreated, so tabs the
  user opens themselves (new-tab button / Cmd+T / open in new tab) are never
  taken over by the BrowserSkill control mask.
- background overlay: decide per-tab state BEFORE showing controls
  (overlayStateForTab + pushOverlayStateForTab) so a user tab receives hidden
  on its first overlay.ready ping instead of flashing control then hiding.
- AgentWindowApi.ensureActiveTab now resolves with the activated/created tab
  id instead of void, so SessionManager can record homeTabId. This fixes the
  tsc failure flagged in review (the interface previously returned
  Promise<void> while callers treated the result as number | null).
- Wire the production tabManagement.tabs / tabsQuery deps into
  tool.session_stop, both in the dispatcher and in the disconnect cleanup.
  They were never injected, which left the agent-tab cleanup and the
  window-release path as dead code outside tests (behaviour identical to
  main). Added a dispatcher-level integration test that fails without the
  wiring: a surviving user tab must release the window, not close it.

apps/extension/src/tools/dispatcher.ts

@@ -66,6 +66,7 @@ import {
 import { chromeTabsApi, lookupSession, resolveTargetTab } from "./shared";
 import {
   type BorrowConfirmationApprover,
+  chromeTabMutationApi,
   handleTabBorrow,
   handleTabClose,
   handleTabCreate,
@@ -298,6 +299,11 @@ export class ToolDispatcher {
         await this.releaseHoverLatch((req.params as SessionStopParams).session_id);
         return handleSessionStop(this.sessions, req.params as SessionStopParams, {
           cdp: this.cdp,
+          // Must be wired in production: the agent-tab cleanup and the
+          // window-release decision (issue #57) read these deps directly
+          // and silently no-op when they are absent.
+          tabManagement: { tabs: chromeTabMutationApi },
+          tabsQuery: chromeTabsApi,
           signal,
         });
       }