fix(actions): exclude workflow_call from workflow trigger detection (#37894)

Gitea now only allows `workflow_dispatch.inputs`. If a workflow contains
`workflow_call.inputs`, the workflow cannot be triggered, even though
the `on:` section contains other trigger events.


https://github.com/go-gitea/gitea/blob/428ee9fcce7928bf5405900345d43e9ba1b01564/modules/actions/jobparser/model.go#L402-L405

For example, this workflow cannot be triggered due to
`workflow_call.inputs`:
```yaml
on:
  push:
  pull_request:
  workflow_call:
    inputs:
      name:
        type: string
```

---

This PR is extracted from #37478 for backport

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.8) <noreply@anthropic.com>
Co-authored-by: Giteabot <teabot@gitea.io>

modules/actions/jobparser/model_test.go

@@ -254,6 +254,53 @@ func TestParseRawOn(t *testing.T) {
 				},
 			},
 		},
+		{
+			// `workflow_call` is only fired by another workflow's `uses:`, so ParseRawOn intentionally excludes it from trigger detection.
+			input: `on:
+  workflow_call:
+    inputs:
+      env:
+        type: string
+        required: true
+    outputs:
+      sha:
+        value: ${{ jobs.build.outputs.commit }}
+    secrets:
+      DEPLOY_KEY:
+        required: true
+`,
+			result: []*Event{},
+		},
+		{
+			// Mixed: a workflow that is both callable AND triggered by push. Only the "push" event surfaces.
+			input: `on:
+  workflow_call:
+    inputs:
+      env:
+        type: string
+  push:
+    branches: [main]
+`,
+			result: []*Event{
+				{
+					Name: "push",
+					acts: map[string][]string{"branches": {"main"}},
+				},
+			},
+		},
+		{
+			// Scalar form: a purely reusable workflow has no event triggers.
+			input:  "on: workflow_call",
+			result: []*Event{},
+		},
+		{
+			// Sequence form: `workflow_call` is excluded while sibling events are kept.
+			input: "on:\n  - push\n  - workflow_call\n  - pull_request",
+			result: []*Event{
+				{Name: "push"},
+				{Name: "pull_request"},
+			},
+		},
 	}
 	for _, kase := range kases {
 		t.Run(kase.input, func(t *testing.T) {