feat(11-01): run job workers in serve and queue:work, add queue:clear

- Manager gains the apparatus JobManager surface: StartJob, UpdateJobState,
  UpdateMetadata, FailJob, CancelJob (is_canceled + STOPPED + River JobCancel),
  StopJob (STOPPED only), CheckIfCanceled and GetMetadata, all raw column
  writes so updated_at is untouched
- serve starts the in-process worker unless queue.work_in_serve is false and
  stops it on shutdown; an app without jobs gets an idle worker
- queue:work runs a foreground worker with repeatable --queue filters;
  queue:clear deletes available, scheduled and retryable jobs of one queue
- the generated main appends conga.RuntimeCommands; summer delegates
  queue:work and queue:clear; make:job scaffolds a conga.Job

internal/build/artifact.go

@@ -192,7 +192,8 @@ func MakeCommand(ctx context.Context, startDir, pluginID, name string) (Artifact
 	return ArtifactResult{PluginDir: plugin.Dir, Files: []string{path}, Hint: plugin.Hint}, nil
 }
 
-// MakeJob writes a pact.Job stub without importing River.
+// MakeJob writes a typed job wrapped in conga.Job; the plugin never
+// imports River.
 func MakeJob(ctx context.Context, startDir, pluginID, name string) (ArtifactResult, error) {
 	plugin, err := resolvePlugin(startDir, pluginID)
 	if err != nil {
@@ -210,10 +211,9 @@ func MakeJob(ctx context.Context, startDir, pluginID, name string) (ArtifactResu
 		return ArtifactResult{}, err
 	}
 	src, err := renderStub("job.go", artifactData{
-		Ident:  name,
-		Func:   fn,
-		Worker: unexportedIdent(name) + "Job",
-		Kind:   plugin.ID + "." + toSnake(name),
+		Ident: name,
+		Func:  fn,
+		Kind:  plugin.ID + "." + toSnake(name),
 	})
 	if err != nil {
 		return ArtifactResult{}, err