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/testdata/uses-composite-with-inputs/action/action.yml

@@ -0,0 +1,29 @@
+name: "action"
+description: "action"
+
+inputs:
+  some:
+    description: "some input"
+    required: true
+  other:
+    description: "other input"
+    default: "${{ inputs.some }}"
+    required: false
+outputs:
+  out:
+    description: "some output"
+    value: "output value"
+
+runs:
+  using: "composite"
+  steps:
+    - run: |
+        echo "action input=${{ inputs.some }}"
+        [[ "${{ inputs.some == 'value' }}" = "true" ]] || exit 1
+      shell: bash
+    - run: |
+        echo "ENV_VAR=$ENV_VAR"
+        [[ "$ENV_VAR" = "value" ]] || exit 1
+      shell: bash
+      env:
+        ENV_VAR: ${{ inputs.other }}

act/runner/testdata/uses-composite-with-inputs/composite/action.yml

@@ -0,0 +1,22 @@
+name: "composite"
+description: "composite"
+
+inputs:
+  composite-input:
+    description: "value"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: test input value
+      run: |
+        echo "input value 1=${{ inputs.composite-input }}"
+        [[ "${{ inputs.composite-input == 'value' }}" = "true" ]] || exit 1
+      shell: bash
+    - uses: nektos/act-test-actions/js@main
+    - name: test input value again
+      run: |
+        echo "input value 2=${{ inputs.composite-input }}"
+        [[ "${{ inputs.composite-input == 'value' }}" = "true" ]] || exit 1
+      shell: bash

act/runner/testdata/uses-composite-with-inputs/push.yml

@@ -0,0 +1,32 @@
+name: push
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - id: set-output
+      run: echo "::set-output name=var::value"
+    - name: use simple composite action
+      uses: ./uses-composite-with-inputs/action
+      with:
+        some: ${{ steps.set-output.outputs.var }}
+    - name: use nested composite action
+      uses: ./uses-composite-with-inputs/composite
+      with:
+        composite-input: value
+    ###
+    #
+    # Remote composite test
+    #
+    - name: use remote composite action
+      id: remote-composite
+      uses: nektos/act-test-actions/composite@main
+      with:
+        input: ${{ steps.set-output.outputs.var }}
+    - name: test remote composite output
+      run: |
+        echo "steps.remote-composite.outputs.output=${{ steps.remote-composite.outputs.output }}"
+        [[ "${{ steps.remote-composite.outputs.output == 'value' }}" = "true" ]] || exit 1
+    #
+    ###