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/tunnel/CHANGELOG.md

@@ -0,0 +1,22 @@
+# Changelog
+
+ - 0.0.6 (2018/09/11)
+   - Fix `localAddress` not working (#25)
+   - Fix `Host:` header for CONNECT method by @tmurakam (#29, #30)
+   - Fix default port for https (#32)
+   - Fix error handling when the proxy send illegal response body (#33)
+
+ - 0.0.5 (2017/06/12)
+   - Fix socket leak.
+ 
+ - 0.0.4 (2016/01/23)
+   - supported Node v0.12 or later.
+
+ - 0.0.3 (2014/01/20)
+   - fixed package.json
+
+ - 0.0.1 (2012/02/18)
+   - supported Node v0.6.x (0.6.11 or later).
+
+ - 0.0.0 (2012/02/11)
+   - first release.