ci: the MRI retry budget went stale the same way JRuby's did

.github/workflows/test.yml

@@ -143,8 +143,8 @@ jobs:
     runs-on: ubuntu-latest
     # Must fit `max_attempts * timeout_minutes` below, plus ~1 min of setup,
     # or the last attempt gets killed mid-run and the cell reports `cancelled`
-    # -- a dead gate. JRuby: 1 + 20 + 20 = 41. MRI: 1 + 3 + 3 = 7, under 8.
-    timeout-minutes: ${{ contains(matrix.ruby-version, 'jruby') && 41 || 8 }}
+    # -- a dead gate. JRuby: 1 + 20 + 20 = 41. MRI: 1 + 4 + 4 = 9.
+    timeout-minutes: ${{ contains(matrix.ruby-version, 'jruby') && 41 || 9 }}
     continue-on-error: ${{ matrix.experimental }}
     strategy:
       matrix:
@@ -212,11 +212,20 @@ jobs:
           # so it was slow, not hung.
           #
           # 20 min restores ~26% over the slowest attempt, which is the margin
-          # this was originally sized for. MRI is 128s against 3 min and does
-          # not move. If JRuby ever exceeds this again, re-measure and raise
-          # BOTH numbers -- a per-attempt timeout that does not fit the job cap
-          # reports `cancelled`, which reads as an absence rather than a fail.
-          timeout_minutes: ${{ contains(matrix.ruby-version, 'jruby') && 20 || 3 }}
+          # this was originally sized for.
+          #
+          # MRI then did the same thing one release later, which is why it is 4
+          # and not 3. "MRI is 128s against 3 min" was true when written; measured
+          # on run 32770212615 the attempts are 78-146s, so the slowest had 23%
+          # left and `3.3/rails81` (144s) duly timed out on run 32889000873 --
+          # again with tests still printing dots when SIGTERM landed. 4 min puts
+          # the slowest back to ~64%.
+          #
+          # The lesson both times: these numbers are measurements, not settings.
+          # When one bites, RE-MEASURE and raise BOTH it and the job cap -- a
+          # per-attempt timeout that does not fit the cap reports `cancelled`,
+          # which reads as an absence rather than a failure.
+          timeout_minutes: ${{ contains(matrix.ruby-version, 'jruby') && 20 || 4 }}
           # Two, not three. A third attempt never fit inside the job cap on
           # either engine (JRuby 3x15=45 > 25; MRI 3x3=9 > 8), so it only ever
           # got killed partway and reported the cell as `cancelled`. Keeping