feat: add /clear command to empty conversation history

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lzwjava

iclaw/main.py

@@ -37,6 +37,7 @@
     ("/ca_bundle", "Set CA bundle for HTTPS (usage: /ca_bundle [path|off])"),
     ("/log", "Set log verbosity (usage: /log [verbose|info])"),
     ("/copy", "Copy last Copilot response to clipboard"),
+    ("/clear", "Clear conversation history"),
     ("/status", "Show current settings"),
     ("/help", "Show available commands"),
     (".exit", "Quit"),
@@ -216,6 +217,11 @@ def main():
             print(f"  cwd:             {os.getcwd()}")
             print()
             continue
+        if user_input == "/clear":
+            messages.clear()
+            last_reply = None
+            print("Conversation history cleared.")
+            continue
 
         if not copilot_token:
             print("Not authenticated. Type /provider_model first.", file=sys.stderr)