Round 26: video probe works; disable WDT autostart + main_loop checkpoint

RESEARCH.md

@@ -1002,3 +1002,37 @@ blue → blinks → hold → green/orange/blue/red/yellow bands → magenta
 (probe entered) → screen CLEARS black → gray (geometry) → cyan/white
 (video clear/probe) → **white-on-black banner** (or a red failure
 band: y=800 lbio, y=820 fmt, y=840 scanout).
+
+## Round 26 — video probe SUCCEEDED (clear ran); post-console hang reset via WDT; WDT disabled for observability
+
+Round 25 (`e4bdd875…`): bands → **screen cleared black** → reset back
+to the depthcharge menu. Decode:
+- The clear proves console env wiring now works: krane.env's
+  stdout=serial,vidconsole → console_init_r → iomux_doenv →
+  console_search_dev("vidconsole") → stdio_probe_device → video
+  driver probed (magenta/gray painted, then erased by the full-screen
+  video_clear) → post-probe cyan/white should have painted too (thin,
+  y=200/260 — possibly missed in the crash window).
+- The reset is the MTK watchdog: CONFIG_WDT_MTK autostarts a 60 s
+  watchdog at initr_watchdog (early board_r); it is serviced by the
+  cyclic scheduler only once main_loop() runs. A hang anywhere between
+  the video probe (still in board_r console init) and the first
+  schedule() → 60 s → WDT reset → depthcharge menu. User's
+  "immediately" = unattended reset.
+
+### Round 26 payload (`08ee5c1f…`, flashed, cmp+vbutil OK)
+
+- **# CONFIG_WATCHDOG_AUTOSTART is not set** — the WDT is probed but
+  not started, so a hang now freezes the screen with bands visible
+  instead of resetting. (Temporary bring-up measure; upstream will
+  want the WDT on.)
+- New checkpoint: **light-gray band (y=900)** at main_loop entry
+  (common/main.c) — everything before it completed.
+
+### Decision tree
+
+| observation | meaning |
+|---|---|
+| black screen stays black, no reset, no gray | hang between video probe and main_loop (console tail / late board_r / initr_mmc...) |
+| black + gray band, frozen | main_loop reached, hang in preboot/cli_init/cli_loop — inspect further |
+| banner + prompt (white on black) | WORKING |