refactor: migrate from github3-py to PyGithub

[jmeridth]

What/Why

Replace github3-py with PyGithub (>=2.6.0) as the GitHub API client library, consolidating on a single actively maintained library across OSPO actions.

Proposed Changes

• pyproject.toml: Swap github3-py for PyGithub>=2.6.0, drop explicit cryptography and pyjwt deps (PyGithub handles JWT internally)
• auth.py: Rewrite to use Auth.Token(), Auth.AppAuth(), GithubIntegration; remove custom RETRY_STRATEGY/REQUEST_TIMEOUT constants and session monkey-patching (_configure_session(), _timeout_wrapper()) in favor of PyGithub's built-in defaults (GithubRetry(total=10), timeout=15)
• Source files (conflict_detector.py, pr_comment.py, pr_data.py, issue_writer.py, pr_conflict_detector.py): Method renames -- repository() to get_repo(), pull_request() to get_pull(), pull_requests() to get_pulls(), issue_comments() to get_issue_comments(), create_comment() to create_issue_comment(), organization() to get_organization(), repositories() to get_repos(), files() to get_files(), team_by_name() to get_team_by_slug(), members() to get_members()
• All test files: Updated mock patterns to match new PyGithub method names
• .github/linters/.mypy.ini: github3.* to github.*

Proof it works

• 283 tests pass with 100% code coverage
• Tested locally with uv run pr_conflict_detector.py

Risk + AI role

Medium -- replaces the core GitHub API client across all modules. All source and test code AI-generated (Claude Opus 4.6).

Review focus

• auth.py: Custom retry/timeout removed; PyGithub's built-in defaults (GithubRetry(total=10), timeout=15) handle transient errors and rate limits out of the box. Verify this is acceptable vs the old 5-retry/30s-timeout strategy.
• Method rename correctness across source and test files.

Readiness Checklist

Author/Contributor

• If documentation is needed for this change, has that been included in this pull request
• run make lint and fix any issues that you have introduced
• run make test and ensure you have test coverage for the lines you are introducing

[Copilot]

Pull request overview

Migrates the action’s GitHub API client from github3-py to PyGithub, updating authentication and all API call sites/mocks accordingly to keep PR conflict detection, issue creation, and PR commenting working with the new client.

Changes:

• Replace github3-py dependency with PyGithub>=2.6.0 and update lockfile accordingly.
• Refactor authentication to use github.Auth/Github/GithubIntegration and pass retry/timeout via constructor kwargs.
• Update all production call sites and unit tests for PyGithub method names (get_repo, get_pull, get_pulls, get_files, etc.) and adjust mypy ignore section.

Show a summary per file

File	Description
uv.lock	Updates locked dependencies to remove github3-py and add pygithub (+ transitive deps).
pyproject.toml	Swaps github3-py/pyjwt/cryptography for PyGithub>=2.6.0.
auth.py	Refactors authentication + app installation token flow to PyGithub APIs and constructor-based retry/timeout.
conflict_detector.py	Migrates verify flow to get_repo()/get_pull() calls.
issue_writer.py	Migrates issue lookup to repo.get_issues(...) and updates type-checking import.
pr_comment.py	Migrates repo/PR/comment APIs to get_repo()/get_pull()/create_issue_comment().
pr_data.py	Migrates PR listing + changed-files retrieval to get_pulls()/get_files()/get_pull().
pr_conflict_detector.py	Migrates repository enumeration + issue creation repo lookup to PyGithub.
.github/linters/.mypy.ini	Updates mypy ignore pattern from github3.* to github.*.
test_auth.py	Updates auth tests to patch PyGithub classes and method names.
test_conflict_detector.py	Updates mocks for get_repo()/get_pull() usage in verification.
test_issue_writer.py	Updates mocks for get_issues() behavior.
test_pr_comment_integration.py	Updates mocks for get_repo() call path.
test_pr_comment_posting.py	Updates mocks for repo/PR comment APIs (get_pull, get_issue_comments, create_issue_comment).
test_pr_conflict_detector_exclude.py	Updates organization/repo mocks to get_organization()/get_repos().
test_pr_conflict_detector_filtering.py	Updates organization/repo mocks to get_organization()/get_repos().
test_pr_conflict_detector_flags.py	Updates organization/repo mocks to get_organization()/get_repos().
test_pr_conflict_detector_main.py	Updates repo/org mocks to get_repo()/get_organization().
test_pr_conflict_detector_repos.py	Updates repo/org iterator tests to get_repo()/get_organization()/get_repos().
test_pr_data.py	Updates PR data mocks to get_pulls()/get_pull()/get_files().

Review details

• Files reviewed: 19/20 changed files
• Comments generated: 5
• Review effort level: Low

[Copilot]

@jmeridth Unfortunately I hit an unexpected error while processing your comment. I've automatically reported this to GitHub.

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[zkoppert]

🚀

[Copilot]

Review details

• Files reviewed: 19/20 changed files
• Comments generated: 3
• Review effort level: Low