docs(display): the mid-panel tear can be compensated; say how, and when it cannot

main's new section called the 1px step at mid-height a panel-scan effect with
nothing to fix in the render path. The scan explanation holds, but at one
pixel per refresh the step is one refresh of motion and lagging one half
cancels it, which this branch does. Rewrite that paragraph, list what
compensation covers and what it leaves to the old advice (held frames,
other layouts, the emulator), and add a CHANGELOG entry.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -194,6 +194,12 @@ floor on the release that ships them):
   `api_extractors`). No known plugin imports it. A plugin that does must use
   `src.common` or its own copy of the code.
 
+- `display.scan_order_compensation` (`"auto"` by default): while something
+  scrolls at one pixel per refresh, one half of each panel is shown a refresh
+  behind the other, which removes the 1px step a 1:N-scan panel shows across
+  its middle. Only for layouts whose row order is known; `"off"` disables it.
+  See `docs/SCROLL_PERFORMANCE.md`, "A tear across the middle on fast scrolls".
+
 ## 3.5.0
 
 New modules a plugin may import via `src.*` (floor on 3.5.0):