Fix alignment-light matrix quant access

[htsugawa]

Summary

• Use the file-backed alignment-light quant accessor when exporting optional alignment matrices. This prevents a KeyNotFoundException when light-mode spots deliberately omit in-memory per-file peak rows.
• Add Console-level two-file Height matrix and accessor regression tests.

Verification on current master

• Merged current origin/master (c471463) into this branch without conflicts.
• MsdialCoreTestAppTests Release: 69 passed, 0 failed.
• AlignmentLightQuantValueAccessorTests Release: 1 passed, 0 failed.
• GitHub PR Check rerun after the merge: passed.
• Existing MessagePack security and zlib compatibility warnings remain unchanged.

This change is independent of automatic alignment RT correction and does not modify normal-mode matrix export.