Refactor breeze pr auto-triage into isolated modules

[potiuk]

Extract the monolithic pr_commands.py (12,400 lines) into 7 focused modules with clean separation of concerns:

• pr_github.py: GitHub API layer (GraphQL/REST, auth, labels, mutations)
• pr_actions.py: Action recommendation and execution with named thresholds
• pr_checks.py: CI check analysis, log parsing, failure detection
• pr_workflows.py: Workflow run management (approve, cancel, rerun)
• pr_authors.py: Author profiling and filtering (AuthorFilter enum)
• pr_fetching.py: GraphQL PR data fetching and assembly
• pr_enrichment.py: PR enrichment, filtering, and categorization pipeline

The most important module is pr_actions.py which encapsulates all decision logic with named constants (AUTHOR_FLAGGED_CLOSE_THRESHOLD, MAX_CI_FAILURES_FOR_RERUN, MAX_COMMITS_BEHIND_FOR_RERUN) replacing magic numbers.

pr_commands.py uses backward-compatible import aliases so all existing code continues to work without modification.

80 new tests added across 5 test files (174 total tests passing).

https://claude.ai/code/session_01JaPYna6Pnw4HMr4t5aCMiL

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