A new `sphinx-vite-builder` package consolidates the workspace's Vite
story into one place with three orthogonal activation paths sharing
one async-subprocess core: a PEP 517 build backend, a hatchling build
hook, and a Sphinx extension. Replaces `gp-sphinx-vite` (deleted) and
fixes the `0.0.1a15` regression where `gp-furo-theme` published
wheels with an empty `static/` tree, leaving docs sites unstyled.

The whole product is the wheel-vs-source asymmetry: a `web/`
directory triggers strict orchestration with fast-fail diagnostics
(`PnpmMissingError`, `NodeModulesInstallError`, `ViteFailedError`,
each carrying a copy-pasteable hint); an absent `web/` (the
unpacked-sdist case) short-circuits cleanly so wheels published to
PyPI need zero toolchain on the consumer side. Errors are
self-healing in CI — detected providers (GitHub Actions, CircleCI,
Azure Pipelines, GitLab CI) get the right setup recipe inlined into
the error message.

**New package — three activation paths:**

- **PEP 517 backend** at `sphinx_vite_builder.build`. Drop-in for
  `hatchling.build`; runs `pnpm exec vite build` before delegating
  wheel/sdist construction.
- **Hatchling build hook** at `[tool.hatch.build.hooks.vite]`. Same
  orchestration via hatchling's plugin system; composes with other
  hatchling hooks.
- **Sphinx extension** registered by `setup()`. One-shot vite build
  under `sphinx-build`; long-running `vite build --watch` under
  `sphinx-autobuild` with graceful SIGTERM→SIGKILL teardown via
  `os.killpg` on the POSIX session group.

**Bug fix — `gp-furo-theme` wheels now ship vite-built CSS and JS.**
`0.0.1a15` published wheels with an empty `static/` because
hatchling's `force-include` rejected the gitignored Vite output;
`sphinx-build` then silently skipped the missing entries. The
backend now builds assets at release time and hatchling packs them
via `[tool.hatch.build] artifacts`.

**Workspace migration.** Consumers using
`merge_sphinx_config(vite_orchestration=True)` continue to work
unchanged — the auto-injection points at `sphinx_vite_builder` now.
Power users with raw `extensions = ["gp_sphinx_vite"]` or
`gp_sphinx_vite_root = ...` in `conf.py` rename to
`sphinx_vite_builder` / `sphinx_vite_builder_root`.

**Released as `0.0.1a16.dev4`.** All workspace packages bumped in
lockstep; `gp-sphinx-vite` retired (issue #32 tracks the manual PyPI
yank).

**Cross-repo validation.** Production deploys verified live across
the consumer corpus — `cihai.git-pull.com`, `libtmux.git-pull.com`,
`tmuxp.git-pull.com`, `vcspull.git-pull.com` and 6 others all serve
the new theme assets (curl against `_static/styles/furo-tw.css`
returns 200 across the board, fixing the `a15` 404 regression).

Breaking changes:
- `gp-sphinx-vite` package retired. Workspace consumers via
  `merge_sphinx_config(vite_orchestration=True)` are unaffected;
  hand-rolled `extensions = ["gp_sphinx_vite"]` callers must rename
  to `"sphinx_vite_builder"`. Config keys renamed:
  `gp_sphinx_vite_{mode,root}` → `sphinx_vite_builder_{mode,root}`.

Closes #28. Closes #30 (Phase 2). Closes #31 (Phase 3). Tracks #32
for the manual PyPI yank.

See also:
- Cross-repo integration: tmux-python/libtmux-mcp#33
- Consumer rollout: cihai/cihai#399, cihai/cihai-cli#348,
  cihai/unihan-db#364, cihai/unihan-etl#356, vcs-python/vcspull#547,
  vcs-python/libvcs#526, vcs-python/g#55, git-pull/gp-libs#69,
  tmux-python/libtmux#666, tmux-python/tmuxp#1037
- maturin (Rust+Cargo analog): https://github.com/PyO3/maturin
- sphinx-theme-builder (webpack analog): https://github.com/pradyunsg/sphinx-theme-builder