fix: stop hiding cached gutter markers while edits refresh

TODO.md

@@ -1,4 +1,3 @@
-- [ ] git gutter flashes on every keystroke/change; this should be fixed.
 - [ ] make all buffers (including pickers) scrolls the window when the cursor reaches a certain threshold. setting could something like "distance from frame edges", and the value could be an integer or none:
 	- "none" would mean "always keep the cursor in the center of the frame" (i.e. scroll the viewport whenever the cursor moves to a different line)
 	- an integer value would be the distance from the edge of the viewport that the cursor must hit before the viewport begins to scroll. a value of 0 means the viewport scrolls only right before the cursor would otherwise have left the viewport; a value greater than half the width of the viewport behaves similarly to "none" (at least until the viewport is resized to support that range in a meaningful way).