refactor: remove agent mode and related functionality; update help and README

src/resources.rs

@@ -8,7 +8,7 @@ Navigation:
   Ctrl+Q       Quit
   Ctrl+H       Help (this screen)
   Ctrl+P       Settings
-  Ctrl+A       Cycle agent mode (Auto/Normal/Plan/Yolo)
+  Ctrl+A       Toggle yolo arm
   Ctrl+B       Bash panel
   Ctrl+S       Session hub
   Ctrl+T       Task list
@@ -18,12 +18,6 @@ Navigation:
   Tab          Autocomplete
   Up/Down      History navigation
 
-Modes:
-  Auto         Automatic approval of most operations
-  Normal       Manual approval for risky operations
-  Plan         Planning mode - no code changes
-  Yolo         Unrestricted - full autonomy
-
 Input:
   /help        Show help
   /clear       Clear screen