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/path-handling/action.yml

@@ -0,0 +1,21 @@
+name: output action
+description: output action
+
+inputs:
+  input:
+    description: some input
+    required: false
+
+outputs:
+  job-output:
+    description: some output
+    value: ${{ steps.gen-out.outputs.step-output }}
+
+runs:
+  using: composite
+  steps:
+    - name: run step
+      id: gen-out
+      run: |
+        echo "::set-output name=step-output::"
+      shell: bash

act/runner/testdata/path-handling/push.yml

@@ -0,0 +1,39 @@
+name: path tests
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: "Append to $GITHUB_PATH"
+        run: |
+          echo "/opt/hostedtoolcache/node/18.99/x64/bin" >> $GITHUB_PATH
+ 
+      - name: test path (after setup)
+        run: |
+          if ! echo "$PATH" |grep "/opt/hostedtoolcache/node/18.*/\(x64\|arm64\)/bin" ; then
+            echo "Node binaries not in path: $PATH"
+            exit 1
+          fi
+
+      - id: action-with-output
+        uses: ./path-handling/
+
+      - name: test path (after local action)
+        run: |
+          if ! echo "$PATH" |grep "/opt/hostedtoolcache/node/18.*/\(x64\|arm64\)/bin" ; then
+            echo "Node binaries not in path: $PATH"
+            exit 1
+          fi
+
+      - uses: nektos/act-test-actions/composite@main
+        with:
+          input: some input
+
+      - name: test path (after remote action)
+        run: |
+          if ! echo "$PATH" |grep "/opt/hostedtoolcache/node/18.*/\(x64\|arm64\)/bin" ; then
+            echo "Node binaries not in path: $PATH"
+            exit 1
+          fi