feat: Add support for dynamic matrix evaluation in Gitea Actions workflows (#36564)

Adds dynamic matrix evaluation to Gitea Actions: a job's
`strategy.matrix` can be built from the outputs of the jobs it needs.

```yaml
jobs:
  generate:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set.outputs.result }}
    steps:
      - id: set
        run: echo "result=[1,2,3]" >> $GITHUB_OUTPUT

  build:
    needs: [generate]
    runs-on: ubuntu-latest
    strategy:
      matrix:
        version: ${{ fromJson(needs.generate.outputs.matrix) }}
    steps:
      - run: echo "building ${{ matrix.version }}"
```

Such a matrix cannot be expanded at planning time, so the job is planned
as a single placeholder and expanded by the job emitter once its needs
finish. Each combination is then gated by `if:` and concurrency as
usual.

- A matrix that resolves to no combination fails the job, as on GitHub.
- Expansion is capped at `MaxJobNumPerRun`.
- Workflows without a needs-dependent matrix are unaffected.

Fixes https://github.com/go-gitea/gitea/issues/25179

---------

Signed-off-by: Pascal Zimmermann <pascal.zimmermann@theiotstudio.com>
Signed-off-by: ZPascal <pascal.zimmermann@theiotstudio.com>
Co-authored-by: Claude <claude-sonnet-4-5@anthropic.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.8) <noreply@anthropic.com>
Co-authored-by: bircni <bircni@icloud.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>

services/actions/run.go

@@ -186,6 +186,7 @@ func InsertRun(ctx context.Context, run *actions_model.ActionRun, content []byte
 func insertRunJob(ctx context.Context, run *actions_model.ActionRun, runAttempt *actions_model.ActionRunAttempt, workflowJob *jobparser.SingleWorkflow, vars map[string]string, inputs map[string]any, slots maxParallelSlots) (*actions_model.ActionRunJob, []*actions_model.ActionRunJob, bool, error) {
 	id, job := workflowJob.Job()
 	needs := job.Needs()
+	isMatrixDeferred := jobparser.HasDeferredMatrix(job)
 	if err := workflowJob.SetJob(id, job.EraseNeeds()); err != nil {
 		return nil, nil, false, err
 	}
@@ -218,8 +219,13 @@ func insertRunJob(ctx context.Context, run *actions_model.ActionRun, runAttempt
 		WorkflowSourceRepoID:    run.WorkflowRepoID,
 		WorkflowSourceCommitSHA: run.WorkflowCommitSHA,
 		ContinueOnError:         job.GetContinueOnError(),
+		IsMatrixDeferred:        isMatrixDeferred,
 		MaxParallel:             parseMaxParallel(id, job.Strategy.MaxParallelString),
 	}
+	if isMatrixDeferred {
+		// Expansion overwrites WorkflowPayload; keep the raw payload so a rerun can re-derive the matrix.
+		runJob.DeferredMatrixPayload = payload
+	}
 	// Parse workflow/job permissions (no clamping here)
 	if perms := ExtractJobPermissionsFromWorkflow(workflowJob, job); perms != nil {
 		runJob.TokenPermissions = perms