fix(ci): bundle _sphinx_html/index.html into wheel (PS-121)

[ywatanabe1989]

Summary

• Seeds the missing in-wheel docs bundle at src/scitex/_sphinx_html/ so PS-121 stops firing
• Also drops src/*/_sphinx_html/ from .gitignore (PS-128) — hatchling's force-include requires the bundle to be tracked
• The package directory is scitex (not scitex_python) so the bundle lives there
• Built locally with sphinx 9.1.0 + the canonical pinned doc stack (sphinx-rtd-theme, myst-parser, sphinx-copybutton, sphinx-autodoc-typehints, plus nbsphinx + matplotlib for the gallery)

PS-121 context

PS-121 in scitex-dev's audit corpus:

package has docs/sphinx/conf.py but no src//_sphinx_html/index.html bundled. scitex-cloud serves docs from the in-wheel _sphinx_html/ — without it the package is invisible at https://scitex.ai/apps/docs/.

Reproducer: scitex-dev ecosystem audit-all scitex-python --no-version-check → PS-121 violation.

PS-128 was also implicitly violated by .gitignore excluding src/*/_sphinx_html/, which would cause hatchling 'Forced include not found' on a clean rebuild.

Note on size

Bundle is ~60 MB due to the matplotlib gallery image set baked into _static/gallery/. .doctrees/ and __intersphinx_cache__/ intermediates have been stripped. The rtd-sphinx-build-on-ubuntu-latest.yml workflow already in place will keep the bundle refreshed on every push to main/develop going forward.

Test plan

• CI quality / audit job passes (no PS-121 violation)
• pip wheel . contains scitex/_sphinx_html/index.html

🤖 Generated with Claude Code

[ywatanabe1989]

Note: the failing pytest-matrix jobs here are blocked on PS-170 (umbrella pin freshness), not anything from this PR:

ERRO: ./pyproject.toml: PS-170: scitex-dev==0.17.4 but PyPI latest is 0.17.6
ERRO: ./pyproject.toml: PS-170: scitex-io==0.2.20 but PyPI latest is 0.2.21
ERRO: ./pyproject.toml: PS-170: scitex-db==0.1.11 but PyPI latest is 0.1.12
ERRO: ./pyproject.toml: PS-170: scitex-msword==0.2.0 but PyPI latest is 0.3.2
ERRO: ./pyproject.toml: PS-170: scitex-dataset==0.3.10 but PyPI latest is 0.4.0

That's a stale umbrella-pin issue that needs a separate chore(deps): bump pinned versions PR — would also be red on a no-op PR right now. This PR only adds files under src/scitex/_sphinx_html/ and removes one line from .gitignore; it can't introduce or worsen the pin-freshness violation.

import-smoke and CLAssistant pass; sphinx, RTD, codecov, etc. are still pending.