M5: the arrow keys move the selected comment

With a comment selected, the arrow keys scrolled the view (↑ ↓) or turned the page (← →), so
a text box, rectangle or line could only be placed with the mouse. Now an arrow key moves the
selected comment a screen pixel, and ⌘/Ctrl or Shift and an arrow ten, as Edit text nudges
objects; up is up on screen whatever the zoom, the page's rotation and the view's. Each press
is one undo step (Edit::MoveAnnotation). The keys are taken before the view's navigation,
which has them back once nothing is selected. Text markup stays with its text, and a locked
comment where it is.

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

parity/acrobat-features.toml

@@ -3971,6 +3971,18 @@ tools = ["comment_delete"]
 evidence = ["crates/ui-egui/tests/it/comments.rs::comments_are_selected_moved_and_deleted_with_the_select_tool", "crates/annot/src/tests.rs::delete_takes_popup_and_reply_chain"]
 notes = "deletes the pop-up and the reply thread"
 
+[[feature]]
+id = "comment.keyboard-nudge"
+title = "Move the selected comment with the arrow keys"
+area = "E"
+tier = "P2"
+milestone = "M5"
+status = "shipped"
+commands = []
+tools = ["comment_edit"]
+evidence = ["crates/ui-egui/tests/it/comments.rs::arrow_keys_nudge_the_selected_comment"]
+notes = "With a comment selected (Select tool, or a Fill & Sign mark picked up), an arrow key moves it a screen pixel and ⌘/Ctrl or Shift and an arrow ten, up being up on screen whatever the zoom and rotation; each press is one undo step, and the arrows scroll and turn pages again once nothing is selected. Text markup stays with its text and a locked comment where it is. Headless, comment_edit's `move` takes the offset in points."
+
 [[feature]]
 id = "comment.reshape"
 title = "Change a line's ends and a polygon's corners after drawing"