feat(render B2): render binder writes user edits into AE before render

Edits previously never reached the MP4 (the node rendered template defaults). Now:
- render-svc claim includes the saved input values as bindings (GetRenderBindings →
  saved_scene_contents with non-empty value).
- node-agent: new binder.go emits a JSON bind-spec + downloads media locally, runs the
  pre-existing data-driven bind.jsx via afterfx (sets text layers' Source Text, replaces
  media footage), saves a bound.aep next to the template, then aerender renders THAT.
- 12-min timeout + fresh-AE + done-marker polling (mirrors scan). Non-fatal: on bind
  failure the job still renders template defaults.

Verified binding data flows (edited frl_c1t1/frl_c1t2 → claim bindings). Live MP4
verification needs the updated node-agent.exe re-run.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/node-agent/cmd/agent/main.go

@@ -424,6 +424,11 @@ func (a *Agent) runJob(ctx context.Context, job *client.ClaimedJob) {
 		}
 	}
 
+	binds := make([]runner.Binding, 0, len(job.Bindings))
+	for _, b := range job.Bindings {
+		binds = append(binds, runner.Binding{Key: b.Key, Type: b.Type, Value: b.Value})
+	}
+
 	rJob := &runner.Job{
 		JobID:          job.JobID,
 		SavedProjectID: job.SavedProjectID,
@@ -434,6 +439,8 @@ func (a *Agent) runJob(ctx context.Context, job *client.ClaimedJob) {
 		HasVoiceover:   job.HasVoiceover,
 		AEPFilePath:    aepPath,
 		CompName:       job.CompName,
+		AfterFxPath:    a.cfg.AfterFxPath,
+		Bindings:       binds,
 	}
 
 	onProgress := func(ctx context.Context, pct int, msg string) error {