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/migrations/migrations.go

@@ -411,6 +411,7 @@ func prepareMigrationTasks() []*migration {
 		newMigration(331, "Add ActionRunAttempt model and related action fields", v1_27.AddActionRunAttemptModel),
 		newMigration(332, "Add last_sync_unix to mirror", v1_27.AddLastSyncUnixToMirror),
 		newMigration(333, "Add bypass allowlist to branch protection", v1_27.AddBranchProtectionBypassAllowlist),
+		newMigration(334, "Add cancelling support to action runners", v1_27.AddCancellingSupportToActionRunner),
 	}
 	return preparedMigrations
 }

models/migrations/v1_27/v334.go

@@ -0,0 +1,17 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_27
+
+import "xorm.io/xorm"
+
+func AddCancellingSupportToActionRunner(x *xorm.Engine) error {
+	type ActionRunner struct {
+		HasCancellingSupport bool `xorm:"has_cancelling_support NOT NULL DEFAULT false"`
+	}
+
+	_, err := x.SyncWithOptions(xorm.SyncOptions{
+		IgnoreDropIndices: true,
+	}, new(ActionRunner))
+	return err
+}

models/migrations/v1_27/v334_test.go

@@ -0,0 +1,36 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_27
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/migrationtest"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestAddCancellingSupportToActionRunner(t *testing.T) {
+	type ActionRunner struct {
+		ID   int64 `xorm:"pk autoincr"`
+		Name string
+	}
+
+	x, deferable := migrationtest.PrepareTestEnv(t, 0, new(ActionRunner))
+	defer deferable()
+	if x == nil || t.Failed() {
+		return
+	}
+
+	_, err := x.Insert(&ActionRunner{Name: "runner"})
+	require.NoError(t, err)
+
+	require.NoError(t, AddCancellingSupportToActionRunner(x))
+
+	var hasCancellingSupport bool
+	has, err := x.SQL("SELECT has_cancelling_support FROM action_runner WHERE id = ?", 1).Get(&hasCancellingSupport)
+	require.NoError(t, err)
+	require.True(t, has)
+	require.False(t, hasCancellingSupport)
+}