ci: job timeout and --blame-hang so a stalled test step fails located, not after 3h of silence (lmxopcua#718)

Run 959 (job 3552) was silent from 13:39 for 3h12m and was failed by the server
reaper with no cause. Pre-#707 runs 935/938/941/942/947/959 all ended at 189-193 min;
no run since 76bdca90 exceeds 82 min (healthy ~53). Adds timeout-minutes 120 and
blame-hang (20m, no dump) to the whole-solution test step.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

.github/workflows/v2-ci.yml

@@ -33,6 +33,11 @@ jobs:
 
   unit-tests:
     runs-on: ubuntu-latest
+    # #718: run 959 sat silent for 3h12m (no log after 13:39) until the server's own ~3h endless-task
+    # reaper failed it, with no hung test named. Every healthy run is ~60 min end to end (test step
+    # ~53 min), so 120 min fails a stall in half the time and cancels the step rather than waiting
+    # for the server reaper.
+    timeout-minutes: 120
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v4
@@ -69,6 +74,9 @@ jobs:
         # — sized on an idle dev box — failed in a long
         # tail, a different test per run. Dilation only stretches waits: a presence wait still fails if
         # the message never comes, and absence windows get longer (stricter). Local runs stay at 1.
+        # #718: --blame-hang kills a test host whose single test makes no progress for 20 min and
+        # NAMES that test in the log (no dump: the runner has no createdump handling), so a hang is a
+        # located failure instead of hours of silence. Healthy tests finish in seconds.
         env:
           AKKA_TEST_TIMEFACTOR: "3"
         run: >
@@ -76,6 +84,7 @@ jobs:
           -m:1 -p:TestTfmsInParallel=false --settings scripts/ci/ci.runsettings
           --filter "Category!=E2E&Category!=LiveIntegration"
           --logger "trx" --results-directory artifacts/trx
+          --blame-hang --blame-hang-timeout 20m --blame-hang-dump-type none
       # 07/S-2 fail-on-skip: a whole-solution run that executed ZERO tests is a masked outage
       # (bad filter, broken discovery), not a pass — fail loudly. Runs even on test failure so
       # the diagnostic is always emitted.