python: build a PyPI-publishable Pyodide (PEP 783) wheel (#9891)

## Summary

z3 already builds under Pyodide (there is a `pyodide.yml` workflow and
an
`IS_PYODIDE` path in `setup.py`), but that path uses `pyodide build` and
produces
a wheel tagged `emscripten_<pyodide-version>_wasm32`, which is pinned to
a single
Pyodide release and rejected by PyPI — so today it's only usable as a CI
artifact.

[PEP 783](https://peps.python.org/pep-0783/) introduced the portable
`pyemscripten_<date>_wasm32` platform tag that **PyPI accepts** and
`micropip` can
install at runtime. This makes `z3-solver` build that wheel via
`cibuildwheel --platform pyodide`.

## Changes

- **`setup.py`** — for the emscripten target, use the wheel platform tag
that
  pyodide-build provides verbatim via `_PYTHON_HOST_PLATFORM` (e.g.
`pyemscripten_2026_0_wasm32`) instead of reconstructing an
`emscripten_*` tag.
  Falls back to the previous behaviour when that env var is absent.
- **`setup.py` / `CMakeLists.txt` / `pyproject.toml`** — switch the
Pyodide build
from JS-based exceptions (`-fexceptions`,
`-sDISABLE_EXCEPTION_CATCHING=0`) to
**native wasm exception handling** (`-fwasm-exceptions
-sSUPPORT_LONGJMP=wasm`),
matching the ABI of the Pyodide 314 / emscripten 5 main module. With the
old
flags `libz3.so` imports `invoke_*` trampolines the runtime no longer
provides,
so the wheel builds but the first `Z3_mk_config` call fails at runtime
with
  `Dynamic linking error: cannot resolve symbol invoke_vi`.
- **`pyproject.toml`** — add `[tool.cibuildwheel]` /
`[tool.pyodide.build]` so
`cibuildwheel --platform pyodide` builds and tests the wheel (`cp314`).
- **`.github/workflows/pyodide-pypi.yml`** (new) — build with
cibuildwheel and
publish to PyPI (trusted publishing) on tags. Existing `pyodide.yml`
unchanged.

## Verification

Built with `cibuildwheel 4.1.0` / `pyodide-build 0.35.0` / `emscripten
5.0.3`,
CPython 3.14 / Pyodide 314:

- Produces `z3_solver-4.17.0.0-py3-none-pyemscripten_2026_0_wasm32.whl`.
- `z3test.py` passes in the Pyodide runtime (node + wasm32).
- Installed via `micropip` and solves SMT problems both under node and
in a
  browser (`sat` with a model, `unsat` for a contradiction).

🤖 Generated with [Claude Code](https://claude.com/claude-code)
🕵️‍♂️ Reviewed by [Alcides Fonseca](https://wiki.alcidesfonseca.com)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

CMakeLists.txt

@@ -204,7 +204,12 @@ elseif (EMSCRIPTEN)
     "-Os"
     "-s ALLOW_MEMORY_GROWTH=1"
     "-s ASSERTIONS=0"
-    "-s DISABLE_EXCEPTION_CATCHING=0"
+    # Use native wasm exception handling + wasm longjmp to match the ABI of the
+    # Pyodide / modern-emscripten main module. The legacy JS-based EH (which the
+    # removed "-s DISABLE_EXCEPTION_CATCHING=0" selected) makes libz3 import
+    # invoke_* trampolines the Pyodide runtime no longer provides.
+    "-fwasm-exceptions"
+    "-s SUPPORT_LONGJMP=wasm"
     "-s ERROR_ON_UNDEFINED_SYMBOLS=1"
   )
 endif()