Migrate package metadata from setup.py to pyproject.toml (PEP 621)

Background

The package metadata still lives in setup.py (name, version, dependencies, extras, entry points, classifiers, etc.). pyproject.toml currently only carries tool configuration (coverage, pytest, mypy, ruff).

With the tox/uv migration landing (see #6325, #6327, #6367, and the rest of the chore/migrate-to-tox-uv work), the distribution itself is the last piece still using legacy setuptools configuration. Moving to PEP 621 [project] metadata would:

• Make the project introspectable by modern tooling (uv sync, uv add, pip install . without executing arbitrary Python, build frontends, dependency scanners, SBOM tools).
• Eliminate the setup.py execution step during builds.
• Align with the direction setuptools itself recommends.

Scope

Port everything currently in setup.py into pyproject.toml:

• [build-system] table (setuptools backend)
• [project] table: name, version, description, readme, requires-python, license, authors, urls, classifiers
• [project] dependencies ← install_requires
• [project.optional-dependencies] ← extras_require (all ~40 extras — names must match exactly; they're public API)
• [project.entry-points.\"opentelemetry_propagator\"] ← entry_points
• [tool.setuptools] zip-safe = false
• [tool.setuptools.package-data] for py.typed (PEP 561)
• [tool.setuptools.packages.find] with tests* excluded
• Verify MANIFEST.in still behaves correctly (or fold into include-package-data)
• Update release tooling (.craft.yml, version-bump scripts) to read/write the version in pyproject.toml instead of setup.py
• Remove setup.py once the above is verified

Verification

• python -m build produces an sdist + wheel byte-identical in contents (modulo metadata format) to the current release
• pip install sentry-sdk[flask], [django], [opentelemetry], etc. resolve identically
• py.typed is shipped in the wheel
• tests/ is not shipped in the wheel
• OTel propagator entry point is discoverable post-install
• Release pipeline dry-run succeeds

Risks

• Public-facing extras names — a typo silently breaks pip install sentry-sdk[name].
• Version bump automation — release tooling likely greps setup.py.
• python_requires=\">=3.6\" in current setup.py looks stale vs. the rest of the repo; worth confirming the intended floor before carrying it forward.

Related

• Tox/uv migration: #6325, #6327, #6367, et al.
• #6121 (removed bdist_wheel universal option)
• #5932 (license classifier inconsistency — pyproject migration is a chance to fix cleanly via license field)