feat: execute post run cleanup when workflow is cancelled (#37275)

## Fixes #36983

## Summary
1. Add transitional `Cancelling` status (between `Running` and
`Cancelled`); cancel flow marks active tasks `Cancelling`, runner
finalizes to `Cancelled` on terminal result.
2. Taskless jobs cancel directly (no runner to finalize).
3. Runner-protocol responses map `Cancelling` → `RESULT_CANCELLED`.
4. Run/job aggregation treats `Cancelling` as active.
5. Status mapping/aggregation tests + en-US locale added.

**Problem**
When a workflow was cancelled from the UI, jobs were marked cancelled
immediately, which could skip post-run cleanup behavior.

## Solution
Use a transitional status path:
Running → Cancelling → Cancelled
This allows runner finalization and cleanup path execution before final
terminal state.

**Testing**

> 1. go test -tags "sqlite sqlite_unlock_notify" ./models/actions -run
"TestAggregateJobStatus|TestStatusAsResult|TestStatusFromResult"
> 2. go run
github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.11.4 run
./models/actions/... ./routers/api/actions/runner/...

## Related
- act_runner: https://gitea.com/gitea/act_runner/pulls/825 —
independent; this PR's capability gate keeps legacy runners on the
immediate-cancel path. The new flow activates only for runners that
advertise the `cancelling` capability.

Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

routers/web/repo/actions/view_test.go

@@ -45,3 +45,34 @@ func TestConvertToViewModel(t *testing.T) {
 	}
 	assert.Equal(t, expectedViewJobs, viewJobSteps)
 }
+
+func TestConvertToViewModelCancellingTaskDoesNotRenderRunningSteps(t *testing.T) {
+	task := &actions_model.ActionTask{
+		Status: actions_model.StatusCancelling,
+		Steps: []*actions_model.ActionTaskStep{
+			{Name: "Run step-name", Index: 0, Status: actions_model.StatusRunning, LogLength: 1},
+		},
+	}
+
+	viewJobSteps, _, err := convertToViewModel(t.Context(), translation.MockLocale{}, nil, task)
+	require.NoError(t, err)
+
+	expectedViewJobs := []*ViewJobStep{
+		{
+			Summary:  "Set up job",
+			Duration: "0s",
+			Status:   "success",
+		},
+		{
+			Summary:  "Run step-name",
+			Duration: "0s",
+			Status:   "cancelling",
+		},
+		{
+			Summary:  "Complete job",
+			Duration: "0s",
+			Status:   "waiting",
+		},
+	}
+	assert.Equal(t, expectedViewJobs, viewJobSteps)
+}