refactor: remove unreachable runner code (#1179)

Remove inherited act APIs, configuration branches, and test seams that neither the daemon nor exec can reach. Constant-fold settings both entry points already enforce and consolidate duplicate runner paths.

Major removals:

- Unwired custom action-cache and local-repository-cache implementations.
- Legacy matrix, platform, input, container-reuse, logging, Git remote, and action-replacement configuration paths.
- Unused Docker socket, container network, tar-copy, and platform PTY wrappers.
- Single-implementation filesystem, environment, runner, and expression abstractions.
- Duplicated step-container, command-logging, credential, reusable-workflow, and execution paths.
- Generated client mock boilerplate, obsolete fixtures, test-only seams, stale wrappers, and commented-out code.

This removes 2844 net Go lines while retaining Gitea RPC, event, matrix, input, cache, artifact, action, reusable workflow, Docker, host, exec, and release behavior.

Assisted by Codex (GPT-5).

Reviewed-on: https://gitea.com/gitea/runner/pulls/1179
Reviewed-by: bircni <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>

act/runner/container_mock_test.go

@@ -14,6 +14,8 @@ import (
 	"github.com/stretchr/testify/mock"
 )
 
+var noopExecutor = func(context.Context) error { return nil }
+
 type containerMock struct {
 	mock.Mock
 	container.Container
@@ -50,11 +52,6 @@ func (cm *containerMock) UpdateFromEnv(srcPath string, env *map[string]string) c
 	return args.Get(0).(func(context.Context) error)
 }
 
-func (cm *containerMock) UpdateFromImageEnv(env *map[string]string) common.Executor {
-	args := cm.Called(env)
-	return args.Get(0).(func(context.Context) error)
-}
-
 func (cm *containerMock) Copy(destPath string, files ...*container.FileEntry) common.Executor {
 	args := cm.Called(destPath, files)
 	return args.Get(0).(func(context.Context) error)