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/job_executor_test.go

@@ -336,6 +336,7 @@ func TestNewJobExecutor(t *testing.T) {
 			executedSteps: []string{
 				"startContainer",
 				"step1",
+				"stopContainer",
 				"interpolateOutputs",
 				"closeContainer",
 			},
@@ -562,9 +563,8 @@ func TestNewJobExecutorRunsPostStepsAfterTimeout(t *testing.T) {
 	jim.On("startContainer").Return(func(ctx context.Context) error { return nil })
 	jim.On("interpolateOutputs").Return(func(ctx context.Context) error { return nil })
 	jim.On("closeContainer").Return(func(ctx context.Context) error { return nil })
-	// The job timed out, so it must be reported as failed. stopContainer is left
-	// unexpected on purpose: a timed-out (failed) job preserves its error state, so
-	// the graceful stop is skipped exactly like any other failure without AutoRemove.
+	// The job timed out, so it must be reported as failed and still cleaned up.
+	jim.On("stopContainer").Return(func(context.Context) error { return nil })
 	jim.On("result", "failure")
 
 	sm := &stepMock{}
@@ -984,12 +984,7 @@ func tarArchive(t *testing.T, entries ...tarEntry) []byte {
 
 func newTestRC(wf *model.Workflow, matrix map[string]any) *RunContext {
 	return &RunContext{
-		Config: &Config{
-			Workdir: ".",
-			Platforms: map[string]string{
-				"ubuntu-latest": "ubuntu-latest",
-			},
-		},
+		Config:      &Config{Workdir: ".", PlatformPicker: func([]string) string { return "ubuntu-latest" }},
 		StepResults: map[string]*model.StepResult{},
 		Env:         map[string]string{},
 		Matrix:      matrix,