pyproject: ship the whole dotbot package so data files reach the wheel

[geonnave]

Reported from a bench session following the cabled LH2 calibration guide:
dotbot run lh2-calibration crashes on a plain pip install pydotbot, and
the workaround was to copy app.tcss out of the repo into
site-packages/dotbot/calibration/ by hand.

The cause is the build allowlist, which enumerated file types:

include = ["dotbot/frontend/*", "dotbot/*.toml", "*.py"]

CalibrationApp sets CSS_PATH = "app.tcss", and nothing in that list
matches .tcss, so the published wheel contains no stylesheet at all. The
same gap dropped every dotbot/examples/ asset - the scene .toml files,
the PNGs and SVGs - so the labyrinth, charging-station and naming-game
examples are also incomplete for anyone installing from PyPI.

Rather than append .tcss to the list and wait for the next data file to
hit the same trap, this ships the package itself. The leading slash is
load-bearing: hatchling patterns are gitignore-style, so a bare dotbot/
also matches nested directories of that name and pulls in a local
doc/_build tree.

twine check validates metadata, not archive contents, so it never had a
chance of catching this. The new utils/check_wheel_contents.py runs right
after it in CI and asserts the wheel carries the data files the code opens
by path; extend REQUIRED when another one is added.

Not addressed here: .gitignore ignores *.xml, so the naming-game
models/*.xml are force-added in git and hatchling still excludes them from
the wheel. That example stays incomplete pending a separate fix.

Validated by building the wheel and inspecting the archive - app.tcss and
the example assets are present, nothing previously shipped was dropped, and
the check fails as intended when the old include list is restored. Full unit
suite passes (414 tests).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.50%. Comparing base (0df33ae) to head (50a2a30).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #282      +/-   ##
===========================================
- Coverage    83.50%   83.50%   -0.01%     
===========================================
  Files          121      121              
  Lines        11237    11266      +29     
  Branches       570      569       -1     
===========================================
+ Hits          9384     9408      +24     
- Misses        1850     1854       +4     
- Partials         3        4       +1     

see 3 files with indirect coverage changes

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[geonnave]

Will merge once @nermine11 confirms it works