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/local-action-via-composite-dockerfile/action.yml

@@ -0,0 +1,44 @@
+inputs:
+  who-to-greet:
+    default: 'Mona the Octocat'
+runs:
+  using: composite
+  steps:
+  # Test if GITHUB_ACTION_PATH is set correctly before all steps
+  - run: stat $GITHUB_ACTION_PATH/push.yml
+    shell: bash
+  - run: stat $GITHUB_ACTION_PATH/action.yml
+    shell: bash
+  - run: '[[ "$GITHUB_ACTION_REPOSITORY" == "" ]] && [[ "$GITHUB_ACTION_REF" == "" ]]'
+    shell: bash
+  - uses: ./actions/docker-local
+    id: dockerlocal
+    with:
+      who-to-greet: ${{inputs.who-to-greet}}
+  - run: '[[ "${{ env.SOMEVAR }}" == "${{inputs.who-to-greet}}" ]]'
+    shell: bash
+  - run: '[ "${SOMEVAR}" = "Not Mona" ] || exit 1'
+    shell: bash
+    env:
+      SOMEVAR: 'Not Mona'
+  - run: '[[ "${{ steps.dockerlocal.outputs.whoami }}" == "${{inputs.who-to-greet}}" ]]'
+    shell: bash
+  # Test if overriding args doesn't leak inputs
+  - uses: ./actions/docker-local-noargs
+    with:
+      args: ${{format('"{0}"', 'Mona is not the Octocat') }}
+      who-to-greet: ${{inputs.who-to-greet}}
+  - run: '[[ "${{ env.SOMEVAR }}" == "Mona is not the Octocat" ]]'
+    shell: bash
+  - uses: ./localdockerimagetest_
+  # Also test a remote docker action here
+  - uses: actions/hello-world-docker-action@v1
+    with:
+      who-to-greet: 'Mona the Octocat'
+  # Test if GITHUB_ACTION_PATH is set correctly after all steps
+  - run: stat $GITHUB_ACTION_PATH/push.yml
+    shell: bash
+  - run: stat $GITHUB_ACTION_PATH/action.yml
+    shell: bash
+  - run: '[[ "$GITHUB_ACTION_REPOSITORY" == "" ]] && [[ "$GITHUB_ACTION_REF" == "" ]]'
+    shell: bash