feat: Improve --install-shortcut to handle existing keybindings

Enhanced install-shortcut to:
- Detect if 'bind a' is already used in tmux config
- Show existing binding and ask user for action
- Allow replacing existing binding or choosing different key
- Support custom keys (e.g., Ctrl+A+B, Ctrl+A+C, etc.)

This prevents conflicts with user's existing tmux configuration.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/autoclaude/cli.py

@@ -462,11 +462,42 @@ class ClaudeCLI:
 
         content = tmux_conf.read_text()
 
-        # Check if already configured
+        # Check if already configured for autoclaude
         if 'autoclaude-toggle' in content:
             self.print_info("Shortcut already configured in ~/.tmux.conf")
             return
 
+        # Check if 'bind a' is already used by something else
+        import re
+        if re.search(r'^\s*bind\s+a\s+', content, re.MULTILINE):
+            self.print_warning("The key 'a' is already bound in your tmux config")
+            self.print_info("Current binding:")
+            for line in content.split('\n'):
+                if re.search(r'^\s*bind\s+a\s+', line):
+                    print(f"  {line.strip()}")
+            print()
+            self.print_info("Options:")
+            print("  1. Replace the existing binding")
+            print("  2. Use a different key")
+            print("  3. Cancel installation")
+            choice = input(f"\n{Colors.BOLD}Choose option (1-3): {Colors.ENDC}")
+
+            if choice == '1':
+                # Remove existing 'bind a' line
+                lines = content.split('\n')
+                lines = [l for l in lines if not re.search(r'^\s*bind\s+a\s+', l)]
+                content = '\n'.join(lines)
+            elif choice == '2':
+                key = input(f"{Colors.BOLD}Enter key to use (e.g., 'b', 'c'): {Colors.ENDC}")
+                if len(key) != 1 or not key.isalpha():
+                    self.print_error("Invalid key. Must be a single letter.")
+                    return
+                # Continue with the custom key
+                return self._add_shortcut_binding(tmux_conf, content, key)
+            else:
+                self.print_info("Installation cancelled")
+                return
+
         # Get the full path to autoclaude-toggle script
         script_path = Path(__file__).parent.parent.parent / '.local' / 'bin' / 'autoclaude-toggle'
         if not script_path.exists():
@@ -476,11 +507,16 @@ class ClaudeCLI:
             self.print_error(f"autoclaude-toggle script not found")
             return
 
+        self._add_shortcut_binding(tmux_conf, content, 'a')
+
+    def _add_shortcut_binding(self, tmux_conf: Path, content: str, key: str):
+        script_path = Path.home() / '.local' / 'bin' / 'autoclaude-toggle'
+
         # Add the keybinding to tmux config
-        binding = f'\n# Toggle autoclaude automation for active pane and show status\nbind a run-shell "{script_path}"\n'
+        binding = f'\n# Toggle autoclaude automation for active pane and show status\nbind {key} run-shell "{script_path}"\n'
 
         tmux_conf.write_text(content + binding)
-        self.print_success(f"Added Ctrl+A+A shortcut to ~/.tmux.conf")
+        self.print_success(f"Added Ctrl+A+{key.upper()} shortcut to ~/.tmux.conf")
         self.print_info("Reload tmux config with: tmux source-file ~/.tmux.conf")
         self.print_info("Or restart your tmux session")