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/internal/runner/runner.go

@@ -37,6 +37,18 @@ type Job struct {
 	// CompName is the composition to render (-comp), e.g. "frfinal". When empty the
 	// node renders the project's render queue (-rqindex 1) instead.
 	CompName string
+	// AfterFxPath is afterfx.exe (the AE app, scriptable) — used by the binder to write
+	// input values into the project before rendering. Render itself uses aerender.exe.
+	AfterFxPath string
+	// Bindings are the user's edited input values to write into the .aep before render.
+	Bindings []Binding
+}
+
+// Binding is one input value written into the AE project before render.
+type Binding struct {
+	Key   string // AE layer/footage name, e.g. frl_c1t1 / frl_c1m1
+	Type  string // content element type (Text, Media, …)
+	Value string // text content, or a media URL
 }
 
 // Run executes the render job, calling onProgress and onPreview as it advances.
@@ -58,6 +70,20 @@ func Run(ctx context.Context, aePath, workDir string, job *Job, onProgress Progr
 		}
 		return mockRender(ctx, job, outputPath, onProgress, onPreview)
 	}
+
+	// Render binder: write the user's edited input values into the project before
+	// rendering so the MP4 reflects their text/media. Non-fatal — on failure we render
+	// the template defaults rather than failing the job.
+	if len(job.Bindings) > 0 && job.AfterFxPath != "" {
+		_ = onProgress(ctx, 6, "Applying your edits…")
+		bound, berr := RunBinder(ctx, job, workDir)
+		if berr != nil {
+			log.Printf("[job %s] binder failed (%v) — rendering template defaults", job.JobID, berr)
+		} else {
+			job.AEPFilePath = bound // render the bound project with the user's values
+		}
+	}
+
 	return aeRender(ctx, aePath, job, outputPath, onProgress, onPreview)
 }