fix(bundle_analysis): Eagerly load base report to handle MissingBaseReportError

[sentry]

This PR addresses issue API-BG6, where MissingBaseReportError was being raised as an internal server error instead of being properly handled and returned as a MissingBaseReport GraphQL union type.

The root cause was that BundleAnalysisComparison.__init__ eagerly loaded self.head_report but not self.base_report. Since base_report is a cached_property, the MissingBaseReportError (triggered when the base report was not found in GCS) was only raised later when resolve_commit_bundle_analysis_compare_with_parent accessed base_report.db_path for cleanup. At this point, the try/except block in load_bundle_analysis_comparison (which is designed to catch this error and return the correct GraphQL type) was no longer active.

The fix involves adding self.base_report = self.comparison.base_report to the BundleAnalysisComparison.__init__ method. This ensures that MissingBaseReportError is triggered during the construction of BundleAnalysisComparison, allowing load_bundle_analysis_comparison to catch it and return the appropriate MissingBaseReport GraphQL type, as intended.

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Fixes API-BG6

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[thomasrockhu-codecov]

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✅ Risk: LOW

This PR adds a single line to BundleAnalysisComparison.__init__ that eagerly loads self.base_report, so a MissingBaseReportError is raised during construction (inside load_bundle_analysis_comparison's try/except) rather than later, correctly returning the MissingBaseReport GraphQL type. The change mirrors the existing eager head_report load and the path is already covered by test_loader_raises_missing_base_report.

No issues found above the confidence threshold.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.63%. Comparing base (17e0f08) to head (6563a7b).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2160   +/-   ##
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  Coverage   91.63%   91.63%           
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  Files        1337     1337           
  Lines       53262    53263    +1     
  Branches     1647     1647           
=======================================
+ Hits        48805    48806    +1     
  Misses       4136     4136           
  Partials      321      321           

Flag	Coverage Δ
apiunit	93.98% <100.00%> (+<0.01%)	⬆️

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