fix: enable multiline paste in web terminal

Multiline pastes into the web terminal (especially into pi) were split
into one prompt per line because bracketed-paste markers were not
reaching the foreground app intact.

- Put the host PTY into raw mode (tty.setraw) after openpty() so it acts
  as a pass-through pipe. The default canonical line discipline was
  line-buffering input, splitting multiline pastes at newlines, and
  mangling bracketed-paste markers before docker exec / pi could see
  them. The in-container PTY (docker exec -t) provides real discipline.
- Route the mobile Paste button through xterm.js (term.paste) instead of
  sending raw clipboard text to the WebSocket, so content is wrapped in
  bracketed-paste markers when the app has enabled BPM.
- Treat a text frame as a control message only when it is a JSON object
  with a known type (resize/ack/reset); otherwise forward as raw input
  so JSON-shaped pastes are no longer silently dropped.

Quality gates: ruff, mypy (changed files), pytest unit (227 passed),
tsc, eslint

apps/api/src/services/terminal/terminal_session.py

@@ -12,6 +12,7 @@ import signal
 import struct
 import fcntl
 import time
+import tty
 import uuid
 from collections import deque
 from typing import Any
@@ -123,6 +124,15 @@ class TerminalSession:
         # Create a pseudo-terminal on the host
         self._master_fd, slave_fd = pty.openpty()
 
+        # Put the host PTY into raw mode so it behaves as a pass-through
+        # pipe. openpty() leaves the slave in canonical mode by default,
+        # which line-buffers input, splits multiline pastes at newlines,
+        # and mangles bracketed-paste markers before docker exec / the
+        # foreground app (e.g. pi) ever see them. Real terminal discipline
+        # (echo, canonical editing for readline) is provided by the
+        # in-container PTY that `docker exec -t` allocates.
+        tty.setraw(slave_fd)
+
         # Set the terminal size initially
         self._set_terminal_size(self._cols, self._rows)
         logger.debug(