[SAMARTHJAISWAL]

Description

Fixes #15281.

For a Jupyter cell, the cap-location option added the class caption-<fig-cap-location value> instead of caption-<cap-location value>, because the block in src/core/jupyter/jupyter.ts read kFigCapLoc. With fig-cap-location unset the cell ended up with caption-undefined. The knitr hook and src/core/handlers/base.ts already use the cap-location value; this changes the Jupyter engine to match.

Tested:

• New smoke test tests/docs/smoke-all/2026/11/12/issue-15281.ipynb: a notebook with stored outputs (execute: enabled: false) with one cell setting cap-location: top plus fig-cap-location: margin, and one cell setting only cap-location: bottom. On main the rendered cells get data-cap-location="margin" and "undefined". With this change they get "top" and "bottom".
• Ran all .ipynb smoke tests locally on main and on this branch. The only difference is the new test, which now passes. The 2 other failures happen on both, because they need Jupyter installed and it isn't on my machine.

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes
• updated the appropriate changelog in the PR
• ensured the present test suite passes
• added new tests
• created a separate documentation PR in Quarto's website repo and linked it to this PR (not needed, bug fix only)

AI-assisted PR

• AI tool used: Claude Code
• Codebase grounding: local clone
• Human review: I have reviewed, tested, and verified the AI-generated content before submitting.

[posit-snyk-bot]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.