row/H3-VISION-SCATTER: scatter vision tower into DiT conditioning (deepstack + merged scatter) - #90

…Stack→device text tower) + ref2va re-attribution

Closes the #86 framework residual and re-attributes the ref2va grid with a GB10
render A/B (row/H3-VISION-SCATTER).

deepstack_visual_indexes CONFIRMED (was #86-inferred): {8,16,24}, grounded in the
release config — MiniMax-H3's text_encoder/ IS Qwen3-VL-32B-Instruct, whose
vision_config.deepstack_visual_indexes = [8,16,24], depth 27, text num_hidden_layers
64 (→50). Same as vllm-omni Qwen3VLMoeVisionConfig default and public
Qwen/Qwen3-VL-30B-A3B. No value change; comment updated.

Deliverable 1 — DEVICE scatter+inject WIRED 1:1 + GATED. MiniMaxH3EncoderTextForwardDevice
now takes the optional visual_pos_mask + per-tap deepstack blocks and ADDS each block
into the masked visual rows after each of the first len(deepstack) decoder layers —
device mirror of the gated host reference and upstream _deepstack_process
(encoder.py:770-800). The merged masked_scatter into inputs_embeds stays the caller's
job (upstream _encode, encoder.py:1071). Text-only prompts pass the defaults and are
byte-identical. Gate: the device keep-quant encoder test now also runs WITH a visual
mask + two DeepStack blocks → device==host max|diff| 3.8e-4 (<=2e-3) AND DeepStack
moves the conditioning (scale 1.006->1.062).

Driver --cond-image routes a reference image through the encoder vision path (reuse
only: Qwen3VLImageProcessor -> Qwen3VLVisionForward -> merged + 3 DeepStack;
ExpandImagePlaceholders inserts nm image-pad tokens; masked_scatter; Qwen3VLGetRopeIndex
== H3 _get_rope_index for t==1, position math verified). Additive.

GB10 render A/B (256x256/22f/12steps):
* Deliverable 3 — fl2va WITH the encoder vision path = COHERENT + matching (PASS):
  frame 0 the keyframe cat, frame 21 the cat on a WINDOWSILL in warm sunlight (evolved
  toward the prompt). No grid. The vision conditioning is SOUND.
* Deliverable 2 — ref2va WITH the vision-enriched prompt STILL GRIDS (honest FAIL):
  same multicolour patch grid as #86's text-only ref2va.

RE-ATTRIBUTION (evidence): the "vision-enriched conditioning fixes the grid"
hypothesis is REFUTED. NOT the encoder conditioning — DiT math byte-exact (#74/#77),
the SAME vision path renders a coherent fl2va, and the grid is invariant to text-only
vs vision-enriched prompts. The only difference between coherent fl2va and gridding
ref2va: fl2va PINS output rows (keyframe), ref2va PREPENDS free-running reference rows.
Residual = the ref2va reference-row conditioning ASSEMBLY (MiniMaxH3EncodeReferenceImages
VAE-reference rows + minimax_h3_packed_sequence_ref2va_blocks noised-anchor layout +
un-pinned target-row denoise), NOT prompt_embeds and NOT the DiT forward.

Records: spec §8.9 + §8.2 row, STATUS/BENCHMARKS/FEATURES H3 rows, benchmark-record,
NOW, state.

FOLLOWING_AGENTS_PROTOCOL
Assisted-by: Claude Code:claude-opus-4-8 [ClaudeCode]