feat(render): Phase 2 — FlexStory render passthrough + journey template seed

Closes the render boundary so a user's scene list (order, per-scene content,
per-scene duration, theme) actually drives the FlexStory engine — the one gap the
scene-engine mapping found.

- render-svc GetFlexStoryProps (db.go): structured per-scene query that groups
  saved_scene_contents BY scene (the flat GetRenderBindings union collides when
  scenes share keys like "title"), recovers blockId from the scene key
  ("<BlockId>__<n>"), and emits the FlexStory props object
  {scenes:[{blockId,durationSec,props}], accentColor, …}.
- render-svc Claim (internal.go): when the template is Remotion + comp starts with
  "FlexStory", send that object as a single "__flexprops__" binding (no protocol
  struct change).
- node-agent remotionProps (remotion.go): if "__flexprops__" is present, pass it
  to `remotion render --props` verbatim (it's the complete props object).
- scripts/seed_flexstory.py: seeds the CharacterJourney template (7 scenes, theme
  colours, FLEXIBLE) with blockId-encoded scene keys, so the studio's existing
  CopyTemplateGraphAsync copies them into saved_scenes with zero studio-svc change.

Both Go services compile; template is live in the catalog (detail 200, per-aspect
previews). End-to-end render verification needs a live Remotion render node.

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

services/node-agent/internal/runner/remotion.go

@@ -57,6 +57,15 @@ func npxCmd() string {
 // (logoText, accentColor, …) and Value is the user's edited string. Anything the
 // user didn't touch falls back to the composition's defaultProps.
 func remotionProps(job *Job) (string, error) {
+	// FlexStory (scene engine) passthrough: the orchestrator already built the full
+	// props object (scenes:[{blockId,durationSec,props}] + theme colours) as a single
+	// "__flexprops__" binding. Use it verbatim — it's a complete JSON object, not a
+	// flat key/value map.
+	for _, b := range job.Bindings {
+		if b.Key == "__flexprops__" {
+			return b.Value, nil
+		}
+	}
 	props := make(map[string]string, len(job.Bindings))
 	for _, b := range job.Bindings {
 		if b.Key == "" {

services/render/internal/db/db.go

@@ -2,6 +2,7 @@ package db
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"strings"
 	"time"
@@ -739,6 +740,108 @@ func (s *Store) GetRenderBindings(ctx context.Context, savedProjectID uuid.UUID)
 	return out, rows.Err()
 }
 
+// GetFlexStoryProps builds the input-props object for a FlexStory (scene-engine)
+// render. Unlike GetRenderBindings (a flat key/value union, which collides when
+// several scenes share a key like "title"), this groups content BY SCENE and
+// returns the structured shape FlexStory expects:
+//
+//	{ "scenes": [ {blockId, durationSec, props:{key:val}}, … ],
+//	  "accentColor": "#…", "secondaryColor": "#…", … }
+//
+// blockId is encoded in the scene key as "<BlockId>__<n>" (n keeps the per-project
+// UNIQUE(key) happy across repeated blocks). Returns a JSON string ready for
+// `npx remotion render … --props=`.
+func (s *Store) GetFlexStoryProps(ctx context.Context, savedProjectID uuid.UUID) (string, error) {
+	type sceneOut struct {
+		BlockID     string            `json:"blockId"`
+		DurationSec float64           `json:"durationSec"`
+		Props       map[string]string `json:"props"`
+	}
+
+	rows, err := s.pool.Query(ctx,
+		`SELECT id, key, scene_length_sec FROM studio.saved_scenes
+		   WHERE saved_project_id = $1 ORDER BY sort`, savedProjectID)
+	if err != nil {
+		return "", err
+	}
+	var scenes []*sceneOut
+	byID := map[int64]*sceneOut{}
+	for rows.Next() {
+		var id int64
+		var key string
+		var dur float64
+		if err := rows.Scan(&id, &key, &dur); err != nil {
+			rows.Close()
+			return "", err
+		}
+		blockID := key
+		if i := strings.Index(key, "__"); i >= 0 {
+			blockID = key[:i]
+		}
+		sc := &sceneOut{BlockID: blockID, DurationSec: dur, Props: map[string]string{}}
+		scenes = append(scenes, sc)
+		byID[id] = sc
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return "", err
+	}
+
+	// per-scene content values → that scene's props
+	crows, err := s.pool.Query(ctx, `
+		SELECT c.saved_scene_id, c.key, COALESCE(c.value, '')
+		  FROM studio.saved_scene_contents c
+		  JOIN studio.saved_scenes s ON s.id = c.saved_scene_id
+		 WHERE s.saved_project_id = $1 AND c.value IS NOT NULL AND c.value <> ''`,
+		savedProjectID)
+	if err != nil {
+		return "", err
+	}
+	for crows.Next() {
+		var sid int64
+		var k, v string
+		if err := crows.Scan(&sid, &k, &v); err != nil {
+			crows.Close()
+			return "", err
+		}
+		if sc := byID[sid]; sc != nil {
+			sc.Props[k] = v
+		}
+	}
+	crows.Close()
+	if err := crows.Err(); err != nil {
+		return "", err
+	}
+
+	out := map[string]any{"scenes": scenes}
+
+	// project-wide theme colours → top-level props (accentColor, …)
+	clr, err := s.pool.Query(ctx,
+		`SELECT element_key, value FROM studio.saved_shared_colors
+		   WHERE saved_project_id = $1 AND value IS NOT NULL AND value <> ''`, savedProjectID)
+	if err != nil {
+		return "", err
+	}
+	for clr.Next() {
+		var k, v string
+		if err := clr.Scan(&k, &v); err != nil {
+			clr.Close()
+			return "", err
+		}
+		out[k] = v
+	}
+	clr.Close()
+	if err := clr.Err(); err != nil {
+		return "", err
+	}
+
+	data, err := json.Marshal(out)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
 func (s *Store) CreateExportForJob(ctx context.Context, jobID uuid.UUID) (*models.Export, error) {
 	// Look up the job to get tenant/user/project context
 	job, err := s.getJobByIDInternal(ctx, jobID)

services/render/internal/handlers/internal.go

@@ -321,7 +321,16 @@ func (h *InternalHandler) Claim(c *gin.Context) {
 
 	// User's edited input values → the node writes them into the AE project before
 	// rendering, or passes them as Remotion --props. Non-fatal: empty → template defaults.
-	bindings, _ := h.store.GetRenderBindings(c.Request.Context(), job.SavedProjectID)
+	// FlexStory (scene engine) needs the structured per-scene shape (grouped by scene
+	// + per-scene duration + theme colours); everything else uses the flat union.
+	var bindings []models.RenderBinding
+	if rcfg.Engine == "Remotion" && strings.HasPrefix(rcfg.CompName, "FlexStory") {
+		if flex, ferr := h.store.GetFlexStoryProps(c.Request.Context(), job.SavedProjectID); ferr == nil && flex != "" {
+			bindings = []models.RenderBinding{{Key: "__flexprops__", Type: "json", Value: flex}}
+		}
+	} else {
+		bindings, _ = h.store.GetRenderBindings(c.Request.Context(), job.SavedProjectID)
+	}
 
 	c.JSON(http.StatusOK, models.ClaimedJob{
 		JobID:          job.ID,