fix: panel handler default returns false for hotkey passthrough

Previously all three panel handlers (forward/plugin/mode) returned
true for unrecognized keys, swallowing Ctrl+Alt+M/F/P/H combos.
Now return false so hotkeys can switch panels without closing.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/tui/panels.go

@@ -145,7 +145,7 @@ func (m *Model) handleForwardPanelKey(key string) bool {
 		m.startForwardForm("Update #"+fmt.Sprint(sel.ID), sel.Mode, sel.Address)
 		return true
 	default:
-		return true
+		return false
 	}
 }
 
@@ -270,7 +270,7 @@ func (m *Model) handlePluginPanelKey(key string) bool {
 		})
 		return true
 	default:
-		return true
+		return false
 	}
 }
 
@@ -321,7 +321,7 @@ func (m *Model) handleModePanelKey(key string) bool {
 		})
 		return true
 	default:
-		return true
+		return false
 	}
 }