some improvements

DESIGN.md

@@ -136,7 +136,7 @@ All are presentations of the same change set for the file:
 3. **Diff**: the editor expands to full screen, covering the other columns. The original file is on the left and the updated file is on the right, lines aligned. `Esc`, or a collapse control in the corner, returns to the normal layout and the previously active mode.
 4. **Preview**: markdown files only. It shows the rendered document instead of the source.
 
-**In Actual, the removed lines appear on hover.** The pointer enters a marked line, and a panel opens over the agent and terminal column: 496px wide, with a 2px amber-deep left border. The panel holds the whole original file, and it scrolls so that the previous version of the hovered line sits level with the hovered line. The pointer leaves the line, and the panel closes. There is no click, no pin, and no animation.
+**In Actual, the removed lines appear on a click.** The user clicks a marked line, and a panel opens over the agent and terminal column: 496px wide, with a 2px amber-deep left border. The panel holds the whole original file, and it scrolls so that the previous version of the picked line sits level with the picked line. A second click on the same line closes the panel, and so does a click anywhere off the code. Hover does nothing, and there is no animation.
 
 Shared rules: teal is what the file holds now, amber-deep is what it held before. There is no green and no red anywhere. Syntax highlighting stays on in all modes. Line numbers follow `editor.lineNumbers` (default absolute).
 
@@ -144,7 +144,7 @@ Shared rules: teal is what the file holds now, amber-deep is what it held before
 
 - A file with no changes opens directly in a normal editable view with no view-mode control, since there is nothing to diff.
 - Editing follows the editor settings: indentation, indent width, trim trailing whitespace, insert final newline, word wrap, indent guides, whitespace rendering, and active-line highlight, all read from configuration (section 10).
-- **Word wrap** follows `editor.wordWrap`: `markdown` (default), `on`, or `off`. When it is on, a line too wide for the pane folds onto the next row instead of scrolling sideways. Only the first row of a folded line carries a line number; the rows below it stay blank. The hover panel folds at the same points as the editor, so each old line stays level with its current line. Diff never wraps, because its two panes align row by row.
+- **Word wrap** follows `editor.wordWrap`: `markdown` (default), `on`, or `off`. When it is on, a line too wide for the pane folds onto the next row instead of scrolling sideways. Only the first row of a folded line carries a line number; the rows below it stay blank. The original panel folds at the same points as the editor, so each old line stays level with its current line. Diff never wraps, because its two panes align row by row.
 
 ### Right-click in code