Fix auto-continue false positives from tool-call-like content

When the LLM outputs text containing tool call patterns (e.g., reading
log files, showing examples, or discussing tool calls), the parser's
has_unexecuted_tool_call() would detect these as real tool calls and
trigger auto-continue, leading to repeated empty responses.

The fix: mark the parser buffer as consumed when content is displayed.
This prevents tool-call-like patterns in displayed text from triggering
false positives later. The fix is safe because:

1. Only runs when no tool was detected (inside 'if !tool_executed')
2. Legitimate tool calls are detected first by process_chunk()
3. Matches existing pattern of calling mark_tool_calls_consumed()
   after tool execution

crates/g3-core/src/lib.rs

@@ -4206,6 +4206,11 @@ impl<W: UiWriter> Agent<W> {
                                     self.ui_writer.print_agent_response(&filtered_content);
                                     self.ui_writer.flush();
                                     current_response.push_str(&filtered_content);
+
+                                    // Mark parser buffer as consumed up to current position
+                                    // This prevents tool-call-like patterns in displayed text
+                                    // from triggering false positives in has_unexecuted_tool_call()
+                                    parser.mark_tool_calls_consumed();
                                 }
                             }
                         }