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/remote-action-js-node-user/push.yml

@@ -0,0 +1,30 @@
+name: remote-action-js
+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    container:
+      image: node:16-buster-slim
+      options: --user node
+    steps:
+    - name: check permissions of env files
+      id: test
+      run: |
+        echo "USER: $(id -un) expected: node"
+        [[ "$(id -un)" = "node" ]]
+        echo "TEST=Value" >> $GITHUB_OUTPUT
+      shell: bash
+
+    - name: check if file command worked
+      if: steps.test.outputs.test != 'Value'
+      run: |
+        echo "steps.test.outputs.test=${{ steps.test.outputs.test || 'missing value!' }}"
+        exit 1
+      shell: bash
+
+    - uses: actions/hello-world-javascript-action@v1
+      with:
+        who-to-greet: 'Mona the Octocat'
+
+    - uses: cloudposse/actions/github/slash-command-dispatch@0.14.0