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/actions/node12/node_modules/tr46/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "tr46",
+  "version": "0.0.3",
+  "description": "An implementation of the Unicode TR46 spec",
+  "main": "index.js",
+  "scripts": {
+    "test": "mocha",
+    "pretest": "node scripts/getLatestUnicodeTests.js",
+    "prepublish": "node scripts/generateMappingTable.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/Sebmaster/tr46.js.git"
+  },
+  "keywords": [
+    "unicode",
+    "tr46",
+    "url",
+    "whatwg"
+  ],
+  "author": "Sebastian Mayr <npm@smayr.name>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/Sebmaster/tr46.js/issues"
+  },
+  "homepage": "https://github.com/Sebmaster/tr46.js#readme",
+  "devDependencies": {
+    "mocha": "^2.2.5",
+    "request": "^2.57.0"
+  }
+}