build: add tauri-essentials extra for buckaroo.server runtime deps

[paddymul]

Summary

Closes #751. Adds [tauri-essentials] — the Python-side runtime deps the buckaroo-tauri integration's sidecar needs to start. Resolves the gap where pip install 'buckaroo[xorq]' (per buckaroo-tauri's README) installs xorq but leaves buckaroo.server unable to import tornado, which #751 walks through in detail.

Distinct from the two existing related extras:

• [xorq] — stat-pipeline only; scoped to XorqStatPipeline per the comment above it. Intentionally does not pull tornado.
• [mcp] — has tornado + polars but not pandas; the sidecar's data_loading.py and session.py both import pandas unconditionally, so [mcp] only "works" today when something else (e.g. the mcp package, or xorq installed alongside) pulls pandas in transitively.

[tauri-essentials] is the minimal explicit set for the sidecar:

tauri-essentials = [
    "tornado>=6.0",
    "polars>=1.24.0",
    "pandas; python_version >= '3.13'",
    "pandas>=1.3.5; python_version < '3.13'",
]

Polars pin matches the existing [polars] extra. Pandas pin matches the existing dual-line pattern from [dev] / [test] / [marimo].

Import audit

buckaroo.server's third-party top-level imports — verified by grepping ^import |^from over buckaroo/server/*.py:

dep	imported by
tornado (ioloop, web, websocket)	__main__.py, app.py, handlers.py, websocket_handler.py
pandas	data_loading.py:4, session.py:6
polars	data_loading.py:5

No other third-party deps. Everything else is stdlib or buckaroo.* internal.

Naming

The name reflects "the Python runtime deps the Tauri integration needs to function" — not the Tauri shim itself (that's buckaroo-data/buckaroo-tauri), and not a dependency on the Tauri framework. See #751 for the discussion.

Test plan

Verified in a fresh 3.12 venv against this branch:

uv venv --python 3.12 /tmp/verify
VIRTUAL_ENV=/tmp/verify uv pip install -e '.[tauri-essentials]' --python /tmp/verify/bin/python
/tmp/verify/bin/python -m buckaroo.server --help
# usage: __main__.py [-h] [--port PORT] [--no-browser]
# Buckaroo data server

• python -c "import tornado, pandas, polars, buckaroo" — all four importable post-install
• python -m buckaroo.server --help — returns clean usage (was ModuleNotFoundError: No module named 'tornado' without the extra)
• tornado==6.5.5, pandas==3.0.3, polars==1.40.1 resolved on 3.12
• CI green

Out of scope (separate follow-ups)

• buckaroo-tauri README update to recommend pip install 'buckaroo[tauri-essentials]' — needs a release of this first.
• Possible deprecation / rename of [mcp] (the contents are generic server deps, the name suggests Model Context Protocol). Flagged in Install command 'pip install buckaroo[xorq]' silently no-ops; sidecar then fails to import tornado #751 as a bonus consideration; not done here.

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[github-actions]

📦 TestPyPI package published

pip install --index-strategy unsafe-best-match --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ buckaroo==0.13.5.dev25991975877

or with uv:

uv pip install --index-strategy unsafe-best-match --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ buckaroo==0.13.5.dev25991975877

MCP server for Claude Code

claude mcp add buckaroo-table -- uvx --from "buckaroo[mcp]==0.13.5.dev25991975877" --index-strategy unsafe-best-match --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ buckaroo-table

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