ci: allow headless in launch-based jobs (e2e, windows-integration)

This fork forbids headless by default (always-headed for stealth, fork.27), but
CI runners have no display, so launched Chrome failed to start — every Native E2E
test errored at 'Chrome Launch attempt failed'. Opt the launch-based jobs into the
documented AGENT_BROWSER_ALLOW_HEADLESS=1 escape (designed for display-less
servers). global-install doesn't launch Chrome, so it's untouched.

.github/workflows/ci.yml

@@ -85,6 +85,11 @@ jobs:
     if: github.event_name != 'pull_request'
     runs-on: ubuntu-latest
     needs: rust
+    # This fork forbids headless by default (always-headed for stealth), but CI
+    # runners have no display. Opt into the documented display-less escape so
+    # launched Chrome can start; e2e tests exercise functionality, not stealth.
+    env:
+      AGENT_BROWSER_ALLOW_HEADLESS: "1"
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
@@ -112,6 +117,10 @@ jobs:
     if: github.event_name != 'pull_request'
     runs-on: windows-latest
     needs: rust-cross
+    # Headless-forbidden fork on a headless CI runner — opt into the escape so
+    # `agent-browser open` can launch Chrome.
+    env:
+      AGENT_BROWSER_ALLOW_HEADLESS: "1"
 
     steps:
       - name: Checkout repository