Harden cleanup and reduce internal RAM use. Phase 8C nearly validated

and somewhat stable.

src/console_completion.h

@@ -9,6 +9,9 @@
 extern "C" {
 #endif
 
+/* Current longest formatted match list is below this; overflow fails closed. */
+#define CONSOLE_COMPLETION_OUTPUT_CAPACITY 1024U
+
 /* Install late-terminal upgrade handling and project-specific completion. */
 void console_completion_install(void);