Merge gitea/act into act/

Merges the `gitea.com/gitea/act` fork into this repository as the `act/`
directory and consumes it as a local package. The `replace github.com/nektos/act
=> gitea.com/gitea/act` directive is removed; act's dependencies are merged
into the root `go.mod`.

- Imports rewritten: `github.com/nektos/act/pkg/...` → `gitea.com/gitea/act_runner/act/...`
  (flattened — `pkg/` boundary dropped to match the layout forgejo-runner adopted).
- Dropped act's CLI (`cmd/`, `main.go`) and all upstream project files; kept
  the library tree + `LICENSE`.
- Added `// Copyright <year> The Gitea Authors ...` / `// Copyright <year> nektos`
  headers to 104 `.go` files.
- Pre-existing act lint violations annotated inline with
  `//nolint:<linter> // pre-existing issue from nektos/act`.
  `.golangci.yml` is unchanged vs `main`.
- Makefile test target: `-race -short` (matches forgejo-runner).
- Pre-existing integration test failures fixed: race in parallel executor
  (atomic counters); TestSetupEnv / command_test / expression_test /
  run_context_test updated to match gitea fork runtime; TestJobExecutor and
  TestActionCache gated on `testing.Short()`.

Full `gitea/act` commit history is reachable via the second parent.

Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>

act/runner/step_factory.go

@@ -0,0 +1,50 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Copyright 2022 The nektos/act Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package runner
+
+import (
+	"fmt"
+
+	"gitea.com/gitea/act_runner/act/model"
+)
+
+type stepFactory interface {
+	newStep(step *model.Step, rc *RunContext) (step, error)
+}
+
+type stepFactoryImpl struct{}
+
+func (sf *stepFactoryImpl) newStep(stepModel *model.Step, rc *RunContext) (step, error) {
+	switch stepModel.Type() {
+	case model.StepTypeInvalid:
+		return nil, fmt.Errorf("Invalid run/uses syntax for job:%s step:%+v", rc.Run, stepModel)
+	case model.StepTypeRun:
+		return &stepRun{
+			Step:       stepModel,
+			RunContext: rc,
+		}, nil
+	case model.StepTypeUsesActionLocal:
+		return &stepActionLocal{
+			Step:       stepModel,
+			RunContext: rc,
+			readAction: readActionImpl,
+			runAction:  runActionImpl,
+		}, nil
+	case model.StepTypeUsesActionRemote:
+		return &stepActionRemote{
+			Step:       stepModel,
+			RunContext: rc,
+			readAction: readActionImpl,
+			runAction:  runActionImpl,
+		}, nil
+	case model.StepTypeUsesDockerURL:
+		return &stepDocker{
+			Step:       stepModel,
+			RunContext: rc,
+		}, nil
+	}
+
+	return nil, fmt.Errorf("Unable to determine how to run job:%s step:%+v", rc.Run, stepModel)
+}