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>

models/actions/status_test.go

@@ -0,0 +1,49 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"testing"
+
+	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStatusAsResult(t *testing.T) {
+	cases := []struct {
+		status Status
+		want   runnerv1.Result
+	}{
+		{StatusUnknown, runnerv1.Result_RESULT_UNSPECIFIED},
+		{StatusWaiting, runnerv1.Result_RESULT_UNSPECIFIED},
+		{StatusRunning, runnerv1.Result_RESULT_UNSPECIFIED},
+		{StatusBlocked, runnerv1.Result_RESULT_UNSPECIFIED},
+		{StatusSuccess, runnerv1.Result_RESULT_SUCCESS},
+		{StatusFailure, runnerv1.Result_RESULT_FAILURE},
+		{StatusCancelled, runnerv1.Result_RESULT_CANCELLED},
+		{StatusCancelling, runnerv1.Result_RESULT_CANCELLED},
+		{StatusSkipped, runnerv1.Result_RESULT_SKIPPED},
+	}
+
+	for _, tt := range cases {
+		assert.Equal(t, tt.want, tt.status.AsResult(), "status=%s", tt.status)
+	}
+}
+
+func TestStatusFromResult(t *testing.T) {
+	cases := []struct {
+		result runnerv1.Result
+		want   Status
+	}{
+		{runnerv1.Result_RESULT_UNSPECIFIED, StatusUnknown},
+		{runnerv1.Result_RESULT_SUCCESS, StatusSuccess},
+		{runnerv1.Result_RESULT_FAILURE, StatusFailure},
+		{runnerv1.Result_RESULT_CANCELLED, StatusCancelled},
+		{runnerv1.Result_RESULT_SKIPPED, StatusSkipped},
+	}
+
+	for _, tt := range cases {
+		assert.Equal(t, tt.want, StatusFromResult(tt.result), "result=%s", tt.result)
+	}
+}