Fix merge results log cache

[jewei1997]

Describe your changes and provide context

• Align cache + parquet rotation to block % MaxBlocksPerFile == 0. Coverage is now derived
  from LatestVersion ([floor(latest/interval)*interval, latest]) instead of tracked in a
  receipt-cache-coverage.json sidecar.
• Fix: empty blocks short-circuited SetReceipts, so rotation never fired when the boundary
  block had zero receipts. Oversized files then got pruned from eth_getLogs queries.
  parquet.Store.ObserveEmptyBlock now rotates on empty-boundary blocks.

Testing performed to validate your change

• TestFilterLogsSurvivesEmptyRotationBoundary /
  TestFilterLogsSurvivesBoundaryThatCrossesFileWidth — regress the empty-boundary bug.
• TestCachedReceiptStoreMergesDuckDBAndCache{AcrossBoundary,ReceiptsAcrossBoundary} — exercise
  the cache+parquet merge path for logs and receipts.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 21, 2026, 2:45 AM

[codecov]

Codecov Report

❌ Patch coverage is 73.25581% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.37%. Comparing base (2900e9a) to head (95cc7ef).

Files with missing lines	Patch %	Lines
sei-db/ledger_db/parquet/store.go	74.54%	8 Missing and 6 partials ⚠️
sei-db/ledger_db/receipt/parquet_store.go	28.57%	3 Missing and 2 partials ⚠️
sei-db/ledger_db/receipt/cached_receipt_store.go	83.33%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3280      +/-   ##
==========================================
+ Coverage   59.35%   59.37%   +0.01%     
==========================================
  Files        2072     2072              
  Lines      169922   169974      +52     
==========================================
+ Hits       100855   100915      +60     
+ Misses      60279    60265      -14     
- Partials     8788     8794       +6     

Flag	Coverage Δ
sei-chain-pr	74.58% <73.25%> (?)
sei-db	70.41% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sei-db/ledger_db/receipt/cached_receipt_store.go	90.71% <83.33%> (+4.73%)	⬆️
sei-db/ledger_db/receipt/parquet_store.go	69.97% <28.57%> (+2.15%)	⬆️
sei-db/ledger_db/parquet/store.go	69.18% <74.54%> (+0.76%)	⬆️

... and 1 file with indirect coverage changes

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