fix: revert docker exec -i change and use stty with line hiding

Reverted docker exec back to -it (required for interactive bash).
Instead, sends stty command with \r to hide it from the terminal display:
- \r moves cursor to start of line (overwrites prompt)
- stty command executes silently (no output on success)
- \r moves cursor back to start, hiding echoed command

This sends stty on EVERY resize so the container shell always matches
frontend dimensions.

apps/api/src/services/terminal_session.py

@@ -61,15 +61,11 @@ class TerminalSession:
         logger.info(f"Starting terminal session {self.session_id} for container {self.container_id} with initial size {self._cols}x{self._rows}")
         
         # Start docker exec with the slave fd as stdin/stdout/stderr
-        # Using -i (interactive) but NOT -t (tty) because:
-        # 1. The slave fd IS a TTY
-        # 2. docker exec -t creates its OWN PTY inside the container
-        # 3. This prevents host PTY resize from propagating to the container shell
-        # By using only -i, docker exec uses our PTY slave directly
+        # Using -it because the slave fd IS a TTY
         self.process = await asyncio.create_subprocess_exec(
             "docker",
             "exec",
-            "-i",
+            "-it",
             "-e",
             "TERM=xterm",
             self.container_id,
@@ -155,6 +151,16 @@ class TerminalSession:
         self._rows = rows
         logger.info(f"resize() called for session {self.session_id}: {cols}x{rows}")
         self._set_terminal_size(cols, rows)
+        
+        # Docker exec -it creates its own PTY inside the container,
+        # so host PTY resize doesn't propagate. We must send stty manually.
+        # To hide the command from the user:
+        # 1. \r moves cursor to start of current line (overwrites prompt)
+        # 2. stty command executes silently (no output on success)
+        # 3. \r moves cursor back to start, hiding the echoed command
+        stty_cmd = f"\rstty cols {cols} rows {rows}\r".encode()
+        await self.write_input(stty_cmd)
+        logger.debug(f"Sent stty resize to container for session {self.session_id}: {cols}x{rows}")
 
     async def reset(self) -> None:
         """Reset the session by killing the process and clearing state."""