feat: expose REINS block-choice in the Editor's Engine Settings

Added a dropdown next to Representation steering strength, not just on
the raw node -- same as every other sampler toggle this project has
shipped.

movie_editor/backend/settings_card.py

@@ -196,6 +196,7 @@ _OWNED_BY = {
     "debug_log": ("identity_transfer_enabled", None),
     "dynashift_strength": ("dynashift", None),
     "dynashift_threshold": ("dynashift", None),
+    "h3_repr_steering_block": ("h3_repr_steering", None),
     "h3_repr_steering_strength": ("h3_repr_steering", None),
     "embed_guidance_source": ("embed_guidance", None),
     "embed_guidance_strength": ("embed_guidance", None),
@@ -267,6 +268,7 @@ _EDITOR_DEFAULTS = {
     "h3_phrase_emphasis": False,
     "h3_phrase_variability": 0.0,
     "h3_repr_steering": False,
+    "h3_repr_steering_block": "25",
     "h3_repr_steering_strength": 0.05,
     "h3_video_detail": 1.0,
     "id_strength": 1.0,

movie_editor/frontend/engine_settings.js

@@ -23,7 +23,7 @@
     "output_guidance", "output_guidance_strength",
     "trajectory_guidance", "trajectory_guidance_strength",
     "dynashift", "dynashift_strength", "dynashift_threshold",
-    "h3_repr_steering", "h3_repr_steering_strength",
+    "h3_repr_steering", "h3_repr_steering_strength", "h3_repr_steering_block",
   ]);
   const RATING_GATED_STUDIO = new Set(["reference_injection", "value_guidance", "steer_mode", "absolute_strength"]);
 
@@ -317,6 +317,8 @@
       hint: "EXPERIMENTAL, unvalidated, H3 only. Reaches inside the model instead of around it: captures one block's video-row hidden state each generation, and once you have 3+ liked and 3+ disliked runs on this refinement key, adds their mean difference back into that block's output on every later run. No architectural ceiling like the attention-bias mechanisms have — push the strength too far and coherence can break with no warning." },
     { name: "h3_repr_steering_strength", label: "Representation steering strength", kind: "float", default: 0.05, min: 0.0, max: 2.0, step: 0.01, dependsOn: "h3_repr_steering",
       hint: "Fraction of the block's own hidden-state norm added along the learned direction. Start low and push it deliberately high on a same-seed test to confirm it moves the video at all before trusting a small value." },
+    { name: "h3_repr_steering_block", label: "Steer at block", kind: "combo", choices: ["20", "25", "30", "35", "40"], default: "25", dependsOn: "h3_repr_steering",
+      hint: "TEST-ONLY: which of the block-sweep's candidate blocks actually gets steered, instead of always block 25. The other candidate blocks are still captured read-only either way." },
     { name: "identity_transfer_enabled", label: "Best-FaceID compatibility", kind: "bool", default: false,
       hint: "Feeds the identity pin image the way Best-FaceID identity LoRAs expect it. Needs an Identity pin set.",
       detail: "Replaces Continuity's identity-pin guide with separate, non-rendered reference tokens plus an optional ArcFace projector below. Load the LoRA itself in Models. No effect without an identity pin." },
@@ -506,7 +508,7 @@
   const CHAIN_VIEW_KNOBS = {
     chain_continuity: ["carry_i2v_guides", "carry_overlap_through_anchor"],
     chain_timing: ["frame_overlap", "transition_duration", "use_same_seed", "cut_opening_frames"],
-    chain_guidance: ["cfg", "embed_guidance", "embed_guidance_source", "embed_guidance_strength", "score_slider", "score_slider_strength", "taste_nearest_prompt", "output_guidance", "output_guidance_strength", "trajectory_guidance", "trajectory_guidance_strength", "dynashift", "dynashift_strength", "dynashift_threshold", "h3_repr_steering", "h3_repr_steering_strength"],
+    chain_guidance: ["cfg", "embed_guidance", "embed_guidance_source", "embed_guidance_strength", "score_slider", "score_slider_strength", "taste_nearest_prompt", "output_guidance", "output_guidance_strength", "trajectory_guidance", "trajectory_guidance_strength", "dynashift", "dynashift_strength", "dynashift_threshold", "h3_repr_steering", "h3_repr_steering_strength", "h3_repr_steering_block"],
     chain_decode: ["decode_noise_scale", "decode_timestep", "decode_tile_size"],
     chain_experimental: ["context_windows", "context_window_length", "context_window_overlap", "context_window_schedule", "context_window_fuse", "context_window_freenoise", "context_window_retain_first", "h3_video_detail", "joyai_memory", "joyai_memory_size", "joyai_fix_frames", "joyai_frame_select", "joyai_memory_strength", "joyai_audio_memory", "v2a_grad_scale", "alg_blur_guides", "alg_guide_blur_strength", "alg_guide_blur_sigma_threshold", "bounded_attention_enabled", "identity_transfer_enabled", "source_id", "phase_scale", "id_strength", "arcface_mode", "debug_log"],
   };