Migrate the W&B quickstart links to Molab

[ktaletsk]

Summary

• Replace the W&B quickstart Colab link with an Open in molab link.
• Point both Molab and GitHub source buttons to run_quickstart.py on the temporary marimo-migration branch.

Dependencies and merge order

This is a stacked draft on top of #3064, which adds the reusable MolabLink component. After #3064 merges, retarget this PR to main.

Counterpart notebook PR: wandb/examples#642.

The examples PR currently deletes run_quickstart.ipynb while adding run_quickstart.py. Therefore this docs PR and wandb/examples#642 should merge together:

• examples first would leave the current Colab and GitHub links pointing to a deleted notebook;
• docs first would point readers at a notebook that exists only on the migration branch.

A less coupled migration would keep run_quickstart.ipynb temporarily in wandb/examples. Then the marimo notebook could merge first, and this docs change could follow independently.

Before merging, update both URLs from marimo-migration to main.

Validation

• mint validate
• mint broken-links
• git diff --check

[github-actions]

Readability impact

Word-weighted Flesch-Kincaid grade change across 1 changed page: +0.0 (unchanged).

Lower Flesch-Kincaid grade and higher reading ease both mean easier to read. This check is informational and never blocks a PR.

Human readability

Page	FK grade before	FK grade after	FK Δ	Reading ease Δ	Direction
models/quickstart.mdx	7.9	7.9	+0.0	+0.0	unchanged

AI agent comprehension

Rated 0-3 (higher is easier for an agent to parse and act on).

Page	Before	After	Δ
models/quickstart.mdx	3	3	+0

_{Curated-docs baseline median FK grade by type: conceptual 10.5, procedural 8.8, reference 9.4.}

From workflow run 31648875673