feat(tui): improve editor Ctrl/Alt word and line deletion shortcuts

- Add Ctrl+W for word deletion (stops at whitespace/punctuation)
- Add Ctrl+U for delete to start of line (merges with previous line at col 0)
- Change Ctrl+K from delete entire line to delete to end of line (merges with next line at EOL)
- Add Option+Backspace support in Ghostty (maps to Ctrl+W via ESC+DEL sequence)
- Cmd+Backspace in Ghostty works as Ctrl+U (terminal sends same control code)
- Update README and CHANGELOG with new keyboard shortcuts

Fixes #2, Fixes #3

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,15 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Editor: updated keyboard shortcuts to follow Unix conventions:
+  - **Ctrl+W** deletes the previous word (stopping at whitespace or punctuation)
+  - **Ctrl+U** deletes from cursor to start of line (at line start, merges with previous line)
+  - **Ctrl+K** deletes from cursor to end of line (at line end, merges with next line)
+  - **Option+Backspace** in Ghostty now behaves like **Ctrl+W** (delete word backwards)
+  - **Cmd+Backspace** in Ghostty now behaves like **Ctrl+U** (delete to start of line)
+
 ## [0.7.8] - 2025-11-13
 
 ### Changed

packages/coding-agent/README.md

@@ -131,7 +131,11 @@ Paste multiple lines of text (e.g., code snippets, logs) and they'll be automati
 
 ### Keyboard Shortcuts
 
-- **Ctrl+K**: Delete current line
+- **Ctrl+W**: Delete word backwards (stops at whitespace or punctuation)
+- **Option+Backspace** (Ghostty): Delete word backwards (same as Ctrl+W)
+- **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)
 - **Ctrl+C**: Clear editor (first press) / Exit pi (second press)
 - **Tab**: Path completion
 - **Enter**: Send message