Move CI to PyPy 3.11, raise minimum Python to 3.11

[vthorsteinsson]

CI is currently red on every leg of the matrix. The cause is a dependency chain, not our code:

sqlalchemy-stubs 0.4  ->  mypy 2.3.0  ->  ast-serialize 0.6.0  (Rust / PyO3)

PyO3's minimum supported Python is 3.11, so installation fails outright before any test runs:

error: the configured PyPy interpreter version (3.10) is lower than
       PyO3's minimum supported version (3.11)

hint: `ast-serialize` (v0.6.0) was included because `sqlalchemy-stubs` (v0.4)
      depends on `mypy` (v2.3.0) which depends on `ast-serialize`

This affects pypy3.9, pypy3.10 and CPython 3.9 alike — it is a floor on the Python version, not a PyPy-specific problem.

Changes

• .github/workflows/python-package.yml: matrix ["3.9", "3.12", "pypy3.9", "pypy3.10"] → ["3.11", "3.12", "pypy3.11"]. Verified that pypy3.11 resolves in the PyPy release index actions/setup-python reads — downloads.python.org/pypy/versions.json lists PyPy 7.3.23 / Python 3.11.15 (2026-05-26) as stable and latest_pypy.
• README.md: badge and stated minimum 3.9 → 3.11; note PyPy 3.11 as the supported PyPy version.
• docs/setup_linux.md: install PyPy 3.11, download URL updated to pypy3.11-v7.3.23-linux64.tar.gz. Note the archive is now .tar.gz — older PyPy releases shipped .tar.bz2.
• docs/setup_macos.md: PyPy 3.9 → PyPy 3.11.
• .gitignore: pypy39/*, pypy310/* → pypy311/*.

Both new URLs verified to return HTTP 200. The workflow YAML parses and the matrix reads back correctly. Scripts under scripts/ reference venv/ generically and need no change.

Deliberately out of scope

vectors/ is untouched. It is a separate CPython environment — currently CPython 3.9.4 with gensim==3.8.2 (a 2019 release), numpy 1.24.3, scipy 1.10.1 — which the main application's minimum does not govern. There is no evidence that stack builds on 3.11, and a gensim 4.x upgrade is an API break (wv.vocab → wv.key_to_index) touching builder.py and the similarity server. Modernising it is separate work.

sqlalchemy-stubs is left in place. Worth noting for a follow-up: it is unmaintained (SQLAlchemy 1.x era), declares mypy as a runtime dependency, and is type-stub-only — no type checker runs in CI, and sqlalchemy2-stubs is already in requirements.txt. Removing it would drop the PyO3 chain entirely and could allow a lower floor, if that is ever wanted.

Known unrelated failure

tests/test_queries.py::test_currency fails on CPython 3.12, where dependencies install successfully. It is independent of the interpreter change and will need fixing separately before the build is fully green.

Production note

This does not move production. /home/greynir/github/Greynir/venv is a symlink to pypy310; switching it means building a fresh PyPy 3.11 venv. Related trap: scripts/deploy.sh lines 51-52 rm venv/site-packages/reynir/Greynir.grammar*.bin works only because the current production venv has an unusual flat layout. A newly built venv will likely use the standard venv/lib/pypy3.11/site-packages/, and those rms will fail silently — set -o errexit is commented out — leaving a stale compiled grammar.

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