Fix editor cursor navigation for wrapped lines, add word navigation

- Up/down arrows now navigate visual (wrapped) lines instead of logical lines
- Fixed double cursor display at wrap boundaries
- Added word by word navigation via Option+Left/Right or Ctrl+Left/Right
- Updated README keyboard shortcuts documentation

Closes #61

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- **Editor Cursor Navigation**: Fixed broken up/down arrow key navigation in the editor when lines wrap. Previously, pressing up/down would move between logical lines instead of visual (wrapped) lines, causing the cursor to jump unexpectedly. Now cursor navigation is based on rendered lines. Also fixed a bug where the cursor would appear on two lines simultaneously when positioned at a wrap boundary. Added word by word navigation via Option+Left/Right or Ctrl+Left/Right. ([#61](https://github.com/badlogic/pi-mono/pull/61))
 - **Edit Diff Line Number Alignment**: Fixed two issues with diff display in the edit tool:
   1. Line numbers were incorrect for edits far from the start of a file (e.g., showing 1, 2, 3 instead of 336, 337, 338). The skip count for context lines was being added after displaying lines instead of before.
   2. When diff lines wrapped due to terminal width, the line number prefix lost its leading space alignment, and code indentation (spaces/tabs after line numbers) was lost. Rewrote `splitIntoTokensWithAnsi` in `pi-tui` to preserve whitespace as separate tokens instead of discarding it, so wrapped lines maintain proper alignment and indentation.

packages/coding-agent/README.md

@@ -517,24 +517,31 @@ Change queue mode with `/queue` command. Setting is saved in `~/.pi/agent/settin
 
 ### Keyboard Shortcuts
 
-- **Ctrl+W**: Delete word backwards (stops at whitespace or punctuation)
-- **Option+Backspace** (Ghostty): Delete word backwards (same as Ctrl+W)
+**Navigation:**
+- **Arrow keys**: Move cursor (Up/Down navigate visual lines, Left/Right move by character)
+- **Option+Left** / **Ctrl+Left**: Move word backwards
+- **Option+Right** / **Ctrl+Right**: Move word forwards
+- **Ctrl+A** / **Home**: Jump to start of line
+- **Ctrl+E** / **End**: Jump to end of line
+
+**Editing:**
+- **Enter**: Send message
+- **Shift+Enter** / **Alt+Enter**: Insert new line (multi-line input)
+- **Backspace**: Delete character backwards
+- **Delete** (or **Fn+Backspace**): Delete character forwards
+- **Ctrl+W** / **Option+Backspace**: Delete word backwards (stops at whitespace or punctuation)
 - **Ctrl+U**: Delete to start of line (at line start: merge with previous line)
-- **Cmd+Backspace** (Ghostty): Delete to start of line (same as Ctrl+U)
 - **Ctrl+K**: Delete to end of line (at line end: merge with next line)
+
+**Completion:**
+- **Tab**: Path completion / Apply autocomplete selection
+- **Escape**: Cancel autocomplete (when autocomplete is active)
+
+**Other:**
 - **Ctrl+C**: Clear editor (first press) / Exit pi (second press)
-- **Tab**: Path completion
 - **Shift+Tab**: Cycle thinking level (for reasoning-capable models)
 - **Ctrl+P**: Cycle models (use `--models` to scope)
 - **Ctrl+O**: Toggle tool output expansion (collapsed ↔ full output)
-- **Enter**: Send message
-- **Shift+Enter**: Insert new line (multi-line input)
-- **Backspace**: Delete character backwards
-- **Delete** (or **Fn+Backspace**): Delete character forwards
-- **Arrow keys**: Move cursor (Up/Down/Left/Right)
-- **Ctrl+A** / **Home** / **Cmd+Left** (macOS): Jump to start of line
-- **Ctrl+E** / **End** / **Cmd+Right** (macOS): Jump to end of line
-- **Escape**: Cancel autocomplete (when autocomplete is active)
 
 ## Project Context Files