[fix](scan) Fix adaptive load batch sizing

[mrhhsg]

Summary

• update file scan load path to feed converted blocks into adaptive batch size prediction before and after varchar truncation
• add debug hooks and regression coverage to make the compact-with-sequence rowset layout reproducible
• keep local regression configuration aligned with the active test cluster

Root Cause

The load path initialized adaptive batch sizing but did not update the predictor after converting loaded source blocks. As a result, the reader could keep using the initial small probe size, creating many small segments and exposing the compaction/delete-bitmap timing issue in unique_with_mow_c_p0/test_compact_with_seq2.

Validation

• git diff --check
• git diff --cached --check
• ./run-regression-test.sh --run -d unique_with_mow_c_p0 -s test_compact_with_seq2

[hello-stephen]

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