feat(renderer): set table download size policy at init

[kirangadhave]

Closes #542

Sets downloadSizeLimitAtom (introduced in marimo PR marimo-team/marimo#9510) to a 50 MB cap with a VS Code–specific message, so the table Export button disables up-front with a tooltip instead of silently failing inside the sandboxed NotebookRenderer.

Why 50 MB

Empirically the sandbox download path and clipboard string limit start failing below 70 MB in testing. 50 MB is the conservative safe ceiling. The size gate uses JSON-serialized size (largest format we support) so if it fits, CSV/Parquet definitely fit.

Screen.Recording.2026-05-12.at.11.28.34.AM.mov

Test plan

• Big table (> 50 MB JSON) in VS Code notebook → Export button disabled, tooltip shows the message
• Small table → Export button enabled, downloads work
• Older marimo backend (no `size_bytes` in render payload) → fail-open, button enabled
• `marimo edit` in browser unaffected (atom not set there)

[github-actions]

Coverage Report

Area	Lines	Branches	Functions
Python	48.17% (503 / 988)	37.97% (101 / 266)	—
TypeScript	unavailable	—	—

[Copilot]

Pull request overview

Updates the VS Code notebook renderer to proactively disable large interactive table exports by configuring marimo’s table download size policy during renderer activation, and bumps the bundled marimo dependency to a newer release.

Changes:

• Bump bundled marimo from 0.23.6 → 0.23.8 (and update lockfile / .marimo-version accordingly).
• Configure downloadSizeLimitAtom in the VS Code renderer to cap table exports at 50 MB with a VS Code–specific tooltip message.
• Re-export downloadSizeLimitAtom/store (and related type) from the typed marimo frontend boundary to allow the renderer to set the policy.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
uv.lock	Updates resolved marimo version and adds new dependency entries introduced by the bump.
pyproject.toml	Pins marimo==0.23.8 for the Python package environment.
extension/src/renderer/renderer.tsx	Sets the table download size policy on activation to disable export for large tables.
extension/src/renderer/marimo-frontend.ts	Adds typed imports/exports for the new download policy atom (and exports store).
.marimo-version	Updates the tracked bundled marimo version to 0.23.8.

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