fix(ci): stop a stalled Codecov upload from cancelling the Coverage job and the main run (main twin of #11972)

Same change as #11972 on release/v3.8.51: the Coverage job had timeout-minutes: 20,
the c8 merge across 8 shards takes ~10 min and the informational Codecov upload hung
for the rest of the budget on two consecutive main runs (33207760653, 33215115341),
ending the job cancelled and turning the run's conclusion cancelled with every
blocking job green. Codecov step: 5-minute ceiling + continue-on-error; job: 30 min.

.github/workflows/ci.yml

@@ -976,7 +976,11 @@ jobs:
     # 10min was sized before #7114 added the lcov reporter (Codecov/Sonar need it);
     # merging 8 shard JSONs + text+json+lcov now takes ~10-12min — three consecutive
     # release-tip runs died at exactly 10m as job-timeout "cancelled" (2026-07-15/16).
-    timeout-minutes: 20
+    # 30, not 20 (2026-08-29): the informational Codecov upload below hung for the rest of
+    # the budget on two consecutive main runs (33207760653, 33215115341); the job ended
+    # `cancelled` and dragged the whole run's conclusion to `cancelled` although every
+    # blocking job was green. The upload step now has its own ceiling; this is headroom.
+    timeout-minutes: 30
     needs: test-unit
     if: ${{ !cancelled() && needs.test-unit.result == 'success' && !contains(github.event.pull_request.labels.*.name, 'hotfix') }}
     env:
@@ -1055,6 +1059,10 @@ jobs:
       # (if-no-files-found: warn) — Sonar consumes the same file.
       - name: Upload coverage to Codecov (informational)
         if: always()
+        # Informational means informational: its own ceiling and continue-on-error, so a
+        # stalled upload can neither eat the job's budget nor turn a green job cancelled.
+        timeout-minutes: 5
+        continue-on-error: true
         uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
         with:
           files: coverage/lcov.info

changelog.d/maintenance/ci-coverage-codecov-step-timeout.md

@@ -0,0 +1 @@
+- `Coverage` job on `ci.yml`: the informational Codecov upload gets its own 5-minute ceiling and `continue-on-error`, and the job budget grows from 20 to 30 minutes (the 8-shard c8 merge alone takes ~10) — a stalled upload no longer ends the job `cancelled` and drags a fully green `main` run's conclusion down with it