Add GitHub issue tests

[gaurav]

This PR introduces a full GitHub-issue-driven test framework for babel-validation. Key additions:

• Assertion framework (src/babel_validation/assertions/) with 8 handler types
• GitHub integration via PyGitHub — parses {{BabelTest|...}} wiki syntax and YAML blocks embedded in issue bodies
• Restructure of shared code from tests/common/ into src/babel_validation/ (library pattern)
• CI workflow running unit tests on PRs
• pytest-xdist parallelism with FileLock-based cache coordination

[Copilot]

Pull request overview

This PR adds a GitHub-issue-driven testing framework to babel-validation by introducing a reusable src/babel_validation/ library (assertion handlers, service wrappers, and test-case sources) and wiring in unit-test CI.

Changes:

• Added an assertions framework (src/babel_validation/assertions/) with auto-generated documentation and a unit test to keep it in sync.
• Added GitHub Issues integration to discover/parse {{BabelTest|...}} and YAML babel_tests: blocks and execute them against NodeNorm/NameRes.
• Added caching/parallelism support (FileLock + xdist) and a GitHub Actions workflow to run unit tests on PRs.

Reviewed changes

Copilot reviewed 26 out of 36 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pyproject.toml	Adds new runtime/test dependencies for GitHub + caching + parallelism.
uv.lock	Locks new dependencies required by GitHub issue framework and xdist.
src/babel_validation/core/testrow.py	Introduces shared TestRow / TestResult types used across sources/assertions.
src/babel_validation/services/nodenorm.py	Adds cached wrapper for NodeNorm normalization calls.
src/babel_validation/services/nameres.py	Adds cached wrapper for NameRes lookup calls.
src/babel_validation/sources/google_sheets/google_sheet_test_cases.py	Moves Google Sheet loader into library + adds local CSV caching.
src/babel_validation/sources/google_sheets/blocklist.py	Extracts blocklist sheet loader into library module.
src/babel_validation/sources/github/github_issues_test_cases.py	Implements GitHub issue search + parsing of embedded BabelTest definitions.
src/babel_validation/assertions/*	Adds assertion handler base classes, NodeNorm/NameRes assertion implementations, and README generator.
tests/github_issues/*	Adds GitHub-issue-driven tests and fixtures, including caching of discovered issue IDs.
tests/test_environment/test_assertions_docs.py	Unit test to enforce auto-generated assertions README is current.
tests/* (various)	Updates imports to use new library modules; minor test data structure cleanup.
tests/pytest.ini	Adds unit marker + timeout configuration (but see comment about config discovery).
.github/workflows/tests.yaml	Adds PR CI job running unit tests via uv run pytest -m unit.
.gitignore	Ignores root .env.
CLAUDE.md	Updates architecture docs to reflect new src/babel_validation/ library and GitHub issues tests.

Comments suppressed due to low confidence (1)

src/babel_validation/sources/google_sheets/google_sheet_test_cases.py:47

• The Google Sheet CSV download is cached to a temp file, but the HTTP response is never validated. If Google returns a non-200 (or an HTML error page), that content will be cached and can make subsequent runs fail in confusing ways. Call response.raise_for_status() (and ideally set a reasonable timeout) before persisting response.text to the cache file.

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