Add example notebooks and notebook docs

[nicosuave]

• add the adtech kitchen sink and Looker-style demo notebooks
• document how to run the notebooks with juv
• note the local extension path the notebooks use when available
• note the fallback to installing yardstick from community

The DuckDB 1.5.x compatibility work remains in #24.

[chatgpt-codex-connector]

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Reviewed commit: f36f5ead59

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[chatgpt-codex-connector]

Point notebook commands to existing files

The new notebook workflow commands reference docs/yardstick_adtech_kitchen_sink.ipynb and docs/yardstick_looker_demo.ipynb, but this repository (including commit 9c6c40b) contains no .ipynb files, so users following these instructions will immediately hit a file-not-found error. Please either add the notebooks or update the commands to paths that exist in-tree.

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[chatgpt-codex-connector]

💡 Codex Review

https://github.com/sidequery/yardstick/blob/5cfa369d8177cd73234b53042db1c566a06ca620/docs/yardstick_adtech_kitchen_sink.ipynb#L4972
Remove trailing literal from notebook JSON

This notebook is not valid JSON because the final line contains a literal \n after the closing brace (}\n), so tools that parse .ipynb (e.g., juv run/Jupyter) fail with Extra data and the example cannot be opened or executed. The second notebook parses correctly, so this is isolated to this file and should be fixed before users rely on the documented command.

ℹ️ About Codex in GitHub

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• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

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