Refresh documentation for the current API

[TheodoreWolf]

Summary

• rewrite the README around the current Random, Grid, and Bayesian search APIs, including accurate batch/buffer semantics, executable examples, JAX constraints, and contributor commands
• add a focused Sphinx usage guide and refresh the optimizer, search-space, acquisition, kernel, and notebook reference pages
• use the README's canonical transparent logo in the Sphinx theme
• remove stale generated API pages that refer to classes which no longer exist
• derive the documentation version from the installed package and remove unused MyST/nbsphinx build dependencies

Verification

• uv run pytest -m 'not timing' -q — 184 passed, 2 deselected
• uv run sphinx-build -W --keep-going -E -a -b html docs/source docs/build/html-main
• parsed every README Python block and executed the quick-start example as written
• verified the rebuilt and live-served theme loads the canonical 949×579 assets/logo-transparent.png

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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