Avoid double formatting in mo.output.replace

[lxingy3]

Summary

Closes #9681

mo.output.replace(value) was formatting value once for the imperative output list and then again when broadcasting the cell output. This reuses the Html object produced for the output list when sending the notification, so expensive _repr_html_ / __panel__ paths only run once.

A regression test covers a probe object whose _repr_html_ increments a counter.

Tests

• python -m pytest tests\_runtime\output\test_output.py -q
• python -m ruff check marimo\_runtime\output\_output.py tests\_runtime\output\test_output.py
• git diff --check

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jun 25, 2026 6:32am

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[lxingy3]

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[lxingy3]

Rebased this on current main to pick up the auth test/dependency fix that was already green upstream.

Local checks:

uv run --group test pytest tests/_runtime/output/test_output.py tests/_server/api/test_auth.py -q
uv run --group dev ruff check marimo/_runtime/output/_output.py tests/_runtime/output/test_output.py tests/_server/api/test_auth.py

The PR diff is still limited to the output replacement fix and its regression test.