fix: console window resize, whiptail clipping and fullscreen height

- FloatingShell: larger default (1000x640), drag-resize handles on all
  8 edges/corners, minimum size enforcement (480x340)
- Terminal: ResizeObserver re-fits xterm whenever container changes size,
  covering both drag-resize and maximize toggle; sends resize WS message
  so PTY tracks the new dimensions
- ssh-execution-service: accept cols/rows params (default 220x50) and
  use them in ptySpawn + COLUMNS/LINES env instead of hardcoded 120x30
- websocket handler: extract cols/rows from start message, pass to
  executeScript; add 'resize' action that calls pty.resize()

src/app/_components/Terminal.tsx

@@ -628,6 +628,8 @@ export function Terminal({
             hostnames,
             containerType,
             envVars,
+            cols: xtermRef.current?.cols ?? 220,
+            rows: xtermRef.current?.rows ?? 50,
           };
           ws.send(JSON.stringify(message));
         }
@@ -711,6 +713,8 @@ export function Terminal({
           cloneCount,
           hostnames,
           containerType,
+          cols: xtermRef.current?.cols ?? 220,
+          rows: xtermRef.current?.rows ?? 50,
         }),
       );
     }