Fix inconsistent collaboration caret heights

The caret height was using 1.2em which is relative to the font-size
of the current context, causing different heights depending on where
the cursor appears in the document.

Changes:
- Changed height from 1.2em to 1em to match actual text height
- Added line-height: inherit to match the line-height of surrounding text
- Added vertical-align: baseline for proper alignment
- Removed min-height: 16px as it's no longer needed

This ensures all collaboration carets have consistent heights that
match the line height of the text where they appear.

Author: jhodapp

src/styles/simple-editor.scss

@@ -395,8 +395,10 @@
   position: relative;
   word-break: normal;
   animation: blink 1.5s infinite;
-  height: 1.2em;
-  min-height: 16px;
+  /* Use line-height to match the actual text height where cursor appears */
+  height: 1em;
+  line-height: inherit;
+  vertical-align: baseline;
   display: inline-block;
 }