chore: add marimo to dev dependencies (#578)

## Summary

Adds [marimo](https://marimo.io) as a dev-extra dependency for notebook
authoring/editing, alongside the existing jupyter-flavored tooling
(`nbformat`, `ruff`, `pre-commit`, etc.).

Added via `uv add --optional dev marimo`, which both updated
`[project.optional-dependencies] dev` in `pyproject.toml` and
regenerated `uv.lock` with the resolved version (`marimo==0.23.6`) and
its transitives. The pin format (`>=0.23.6`) matches the existing
convention for entries in the dev list.

## Test plan

- [x] `uv sync --extra dev` succeeds locally
- [x] `uv lock --check` passes
- [x] `uv run marimo --version` → `0.23.6`
- [ ] CI: `lint` green
- [ ] CI: `test-notebooks-changed` no-op (no `.ipynb` changes)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: this only updates development dependencies/lockfile and
doesn’t change runtime code paths or application logic.
> 
> **Overview**
> Adds `marimo>=0.23.6` to the `dev` optional dependency set in
`pyproject.toml`.
> 
> Regenerates `uv.lock` to include `marimo==0.23.6` and its newly
resolved transitive packages (e.g., `starlette`, `uvicorn`,
`websockets`, `pyzmq`, etc.).
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
9bdb770. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: jhamon

pyproject.toml

@@ -17,6 +17,7 @@ dev = [
     "pre-commit>=4.0",
     "ruff>=0.9",
     "click>=8.3",
+    "marimo>=0.23.6",
 ]
 
 [tool.uv]