ci: take CodeQL and E2E off the per-merge push path (#5859)

After #5842, CodeQL and the E2E suite were the only things running on every push to `main` — the per-commit, post-merge backstop. With merges landing back-to-back, those runs (CodeQL ~30min, three E2E jobs ~25/36/36min, the latter never cancel-superseded) stacked on the scarce hosted Linux pool and were a main driver of the recent runner-saturation incident.

- CodeQL moves to its own scheduled codeql.yml (nightly + workflow_dispatch). It was never a required check and findings still surface in the Security tab, so per-commit scanning bought little. ci.yml loses its now-empty `push` trigger as a result (every remaining job is gated to pull_request / merge_group).
- E2E gets event-scoped concurrency so back-to-back pushes to `main` cancel superseded runs (only the latest tree matters and it covers every merged change), plus a nightly full regression as the guaranteed signal in case a busy merge window keeps cancelling the push run. Manual workflow_dispatch added.

The merge_group gate (ubuntu + integration + mac + win) still validates every PR before it lands; this only changes the non-gating post-merge work.

Follow-up (separate PR): alert on E2E/CodeQL failure (a deduped ci-failure issue) now that they run unattended.

.github/workflows/ci.yml

@@ -3,12 +3,10 @@
 name: 'Qwen Code CI'
 
 on:
-  push:
-    branches:
-      - 'main'
-      # No 'release/**' here: release.yml's commits to the release branch would
-      # fire a redundant full CI run that blocks the release PR's merge queue.
-      # Kept under pull_request below for backport PRs.
+  # No `push` trigger: every job here is gated to pull_request / merge_group, so
+  # a push to `main` ran nothing (CodeQL was the last push job and moved to its
+  # own scheduled codeql.yml). The merge queue validates the merged tree before
+  # it lands, so there is nothing left to run on the post-merge push.
   pull_request:
     branches:
       - 'main'
@@ -430,36 +428,6 @@ jobs:
           os: '${{ matrix.os }}'
           github_token: '${{ secrets.GITHUB_TOKEN }}'
 
-  codeql:
-    name: 'CodeQL'
-    needs: 'classify_pr'
-    # Security findings rarely change push-to-push, and a slow scan is poor value
-    # as a hard merge gate. Run CodeQL only on push to `main` (post-merge
-    # backstop) — not on PR pushes, and not in the merge queue where, being
-    # non-required, it would just burn a runner and lengthen the serial queue
-    # without blocking anything.
-    if: "${{ !cancelled() && needs.classify_pr.outputs.skip_ci != 'true' && github.event_name != 'pull_request' && github.event_name != 'merge_group' }}"
-    runs-on: 'ubuntu-latest'
-    # Analysis normally finishes in ~7-9 min (22 min worst case observed). Without
-    # an explicit cap, a hosted runner that drops its heartbeat mid-analysis leaves
-    # the job "in_progress" for the default 6h, holding a scarce hosted Linux slot
-    # the whole time. 30 min reaps such an orphan fast while clearing real runs.
-    timeout-minutes: 30
-    permissions:
-      actions: 'read'
-      contents: 'read'
-      security-events: 'write'
-    steps:
-      - name: 'Checkout'
-        uses: 'actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd' # v6.0.2
-
-      - name: 'Initialize CodeQL'
-        uses: 'github/codeql-action/init@df559355d593797519d70b90fc8edd5db049e7a2' # ratchet:github/codeql-action/init@v3
-        with:
-          languages: 'javascript'
-
-      - name: 'Perform CodeQL Analysis'
-        uses: 'github/codeql-action/analyze@df559355d593797519d70b90fc8edd5db049e7a2' # ratchet:github/codeql-action/analyze@v3
 
   # Integration tests run only in the merge queue, not on every PR push.
   # They are the suite that previously ran *only* in the nightly Release

.github/workflows/codeql.yml

@@ -0,0 +1,41 @@
+name: 'CodeQL'
+
+# CodeQL used to be a per-push job in ci.yml. Security findings rarely change
+# commit-to-commit and the scan is non-blocking (never a required check), so
+# running it on every merge to `main` just piled onto the scarce hosted Linux
+# pool. Run it on a nightly schedule (plus manual dispatch) instead; findings
+# still surface in the Security tab. If fresher results are wanted, add a
+# path-filtered `push` trigger for security-relevant sources.
+on:
+  schedule:
+    - cron: '0 3 * * *' # nightly (~03:00 UTC), staggered from the E2E nightly
+  workflow_dispatch:
+
+permissions:
+  actions: 'read'
+  contents: 'read'
+  security-events: 'write'
+
+concurrency:
+  group: 'codeql'
+  cancel-in-progress: false
+
+jobs:
+  codeql:
+    name: 'CodeQL'
+    runs-on: 'ubuntu-latest'
+    # Analysis normally finishes in ~7-9 min (22 min worst case observed). Cap it
+    # so a runner that drops its heartbeat mid-analysis can't hold a slot for the
+    # default 6h.
+    timeout-minutes: 30
+    steps:
+      - name: 'Checkout'
+        uses: 'actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd' # v6.0.2
+
+      - name: 'Initialize CodeQL'
+        uses: 'github/codeql-action/init@df559355d593797519d70b90fc8edd5db049e7a2' # ratchet:github/codeql-action/init@v3
+        with:
+          languages: 'javascript'
+
+      - name: 'Perform CodeQL Analysis'
+        uses: 'github/codeql-action/analyze@df559355d593797519d70b90fc8edd5db049e7a2' # ratchet:github/codeql-action/analyze@v3

.github/workflows/e2e.yml

@@ -1,25 +1,30 @@
 name: 'E2E Tests'
 
 on:
-  # E2E runs post-merge on `main` (per-commit signal) only. It is intentionally
-  # NOT in the merge queue yet: it is slow and currently flaky, so gating the
-  # serial queue on it would stall every merge. Promote it to `merge_group` +
-  # required once it is reliable.
+  # E2E is slow and currently flaky, so it is NOT in the merge queue (gating the
+  # serial queue on it would stall every merge). It runs post-merge on `main`,
+  # plus a nightly full regression and on-demand. Promote it to `merge_group` +
+  # required once a stable subset is carved out.
   push:
     branches:
       - 'main'
       - 'feat/e2e/**'
+  schedule:
+    - cron: '0 4 * * *' # nightly full regression (~04:00 UTC), guaranteed signal
+  workflow_dispatch:
 
 concurrency:
-  # Key on the head ref so a `push` to a `feat/e2e/**` branch and a
-  # `pull_request` from that same branch share one group and cancel each
-  # other instead of running the matrix twice for the same change.
+  # Scope the group by event so back-to-back pushes to `main` cancel superseded
+  # runs (no pile-up when PRs merge in quick succession), without ever cancelling
+  # the nightly schedule or a manual dispatch — they share the ref but not the
+  # event. feat/e2e/** pushes still cancel their own superseded runs.
   group: |-
-    ${{ github.workflow }}-${{ github.head_ref || github.ref_name }}
-  # Cancel superseded feature-branch runs, but let every `main` commit finish
-  # (complete per-commit e2e signal, matching ci.yml).
+    ${{ github.workflow }}-${{ github.event_name }}-${{ github.head_ref || github.ref_name }}
+  # Cancel superseded pushes (main included now — only the latest tree matters,
+  # and it covers every merged change). The nightly run always finishes, so a
+  # busy merge window that keeps cancelling the push run still gets a signal.
   cancel-in-progress: |-
-    ${{ github.event_name == 'push' && github.ref != 'refs/heads/main' }}
+    ${{ github.event_name == 'push' }}
 
 jobs:
   e2e-test-linux: