ci: add PyPI trusted publishing (abi3 wheels, v0.2.1) (#123)

* ci: add PyPI trusted publishing, abi3 wheels, bump to 0.2.1

Adds publish-pypi.yml mirroring the npm/crates.io pattern: triggers on
Cargo.toml version change, builds wheels for 5 platforms via maturin,
publishes with OIDC trusted publishing (no tokens). workflow_dispatch
serves as a manual fallback for the first run after the PyPI project
transfer.

Enables pyo3 abi3-py38 so one wheel per platform covers CPython >=3.8
(previous manual uploads were cp312-only). Bumps version to 0.2.1 since
PyPI already has 0.2.0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* ci(pypi): guard dispatch to main, support partial-release repair

Review feedback: trusted publishing doesn't match on branch, so
workflow_dispatch needed an explicit main-ref guard. Manual dispatch now
always rebuilds and publishes with skip-existing so a release that
failed after uploading only some wheels can be completed by re-running.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* ci(pypi): version PyPI package from pyproject.toml, not Cargo.toml

Decouple the Python package version from the crate version, matching
how npm publishing keys off napi/package.json: bump [project] version
in pyproject.toml manually and CI publishes on merge. Reverts the
Cargo.toml bump so this PR no longer triggers a crates.io release.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* chore: remove accidentally committed uv.lock

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(ci): tolerate missing version key in parent pyproject.toml

The first merge of this workflow has a parent commit where pyproject.toml
still used dynamic = ["version"], so the old-version read would KeyError
and the auto-publish would never fire. Treat a missing key as a change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Cargo.toml

@@ -14,7 +14,7 @@ crate-type = ["lib", "cdylib"]
 
 [dependencies]
 # Python bindings
-pyo3 = { version = "0.25", features = ["extension-module"], optional = true }
+pyo3 = { version = "0.25", features = ["extension-module", "abi3-py38"], optional = true }
 
 # PDF parsing
 lopdf = { version = "0.41.0", features = ["rayon"] }