[rtc_v2] Markdown cells phantom typing

[akshayka]

Describe the bug

• Running with rtc_v2
• Two tabs open to the same notebook, both in edit view.
• When attempting to edit a markdown cell, the cell gets populated with gibberish text as I type. Here is an example of the text that was entered.

Environment

{
  "marimo": "0.13.2",
  "OS": "Linux",
  "OS Version": "6.8.0-58-generic",
  "Processor": "x86_64",
  "Python Version": "3.13.0",
  "Binaries": {
    "Browser": "135.0.7049.114",
    "Node": "v18.13.0"
  },
  "Dependencies": {
    "click": "8.1.8",
    "docutils": "0.21.2",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.8",
    "narwhals": "1.36.0",
    "packaging": "25.0",
    "psutil": "7.0.0",
    "pygments": "2.19.1",
    "pymdown-extensions": "10.14.3",
    "pyyaml": "6.0.2",
    "starlette": "0.46.2",
    "tomlkit": "0.13.2",
    "typing-extensions": "missing",
    "uvicorn": "0.34.2",
    "websockets": "15.0.1"
  },
  "Optional Dependencies": {
    "pycrdt": "0.11.1",
    "ruff": "0.11.7"
  },
  "Experimental Flags": {
    "lsp": true,
    "rtc_v2": true,
    "chat_sidebar": true,
    "multi_column": true
  }
}

Code to reproduce

No response