Round 20: video_clear reached; cyan/white two-band instrumentation

RESEARCH.md

@@ -784,3 +784,33 @@ stands as the only black-producing mechanism.)
 | black + white band | video probe completed; died between post_probe and banner |
 | black, no white band | died inside video_post_probe after video_clear (bind/probe of vidconsole) |
 | banner (white on black) | works |
+
+## Round 20 — post-probe black decoded: U-Boot reaches video_clear; two-band instrumentation
+
+Round 19 (`1f598c7a…`): wrapper color + blinks, then **black, no white
+band**. Decoded: U-Boot runs (correct alignment), reaches the video
+uclass `video_clear()` (the only black-painter — that's the blue→black
+transition), and dies/ends before the white band at the end of
+video_post_probe. The window contains only: colours setup, vidconsole
+bind ("vidconsole0"), device_probe of the console child, cyclic
+registration. A GRACEFUL failure there (bind/probe error → video probe
+fails) leaves exactly the observed state: cleared black, no banner
+(goes nowhere — no console), backlight on. Also noted: CONFIG_CYCLIC=y
+makes video-uclass line 732's `gd->flags && GD_FLG_RELOC` typo live
+(harmless-looking cyclic_register every 10 ms).
+
+### Round 20 payload (`90f0de99…`, flashed, cmp+vbutil OK)
+
+Two-band instrumentation inside video_post_probe:
+- **cyan** band right after `video_clear()` — visible ⇒ the clear and
+  the fb mapping work, death is later in this function or after;
+- **white** band after the vidconsole child is bound+probed (existing).
+
+### Decision tree
+
+| observation | meaning |
+|---|---|
+| black only (no cyan) | died between clear and cyan — video_set_default_colors/... (near-impossible) |
+| cyan only | death/graceful-failure in bind or probe of vidconsole0 |
+| cyan + white | died between post_probe end and the banner (jumptable/console_init_r/puts) |
+| banner | works |