fix(rootmulti): stop snapshot restore when node is rejected by SC importer

[manav2401]

Snapshot restore now exit early when the SC (State Commitment) importer cannot import a node, instead of continuing without it. Previously the FlatKV importer skipped such nodes silently, while the restore still passed them on to the SS (State Store).

• Importer.AddNode now returns an error. KVImporter rejects non-leaf nodes, nodes without a key, and nodes at a version other than the import height, instead of skipping them.
• rootmulti.Store.restore stops on that error, and forwards a leaf to the state store only after SC accepts it.
• The memiavl importer always returns nil, the composite importer returns its backend's error, and seidb import-flatkv-from-memiavl stops at the first rejected pair.

[cursor]

PR Summary

High Risk
Changes snapshot restore and FlatKV import validation on consensus-critical state paths; a malformed or version-mismatched node now aborts restore instead of partially applying SS data.

Overview
Snapshot restore now fails fast when the state-commitment (SC) importer rejects a node, instead of continuing and still feeding leaves to the state store (SS).

Importer.AddNode returns an error across the SC stack. FlatKV’s KVImporter rejects (rather than silently skips) non-leaf nodes, empty keys, version mismatches, and empty physical values; a failed import does not finalize. The composite importer surfaces the active backend’s error; memiavl’s importer adopts the same signature.

rootmulti.Store.restore checks scImporter.AddNode and aborts the restore loop on failure; SS import runs only for leaves SC already accepted. The import-flatkv-from-memiavl tool propagates the first AddNode failure from emitPairs.

Tests cover wrong-version flatkv snapshots end-to-end, partial SS import on mid-stream rejection, and importer version/empty-key behavior.

^{Reviewed by Cursor Bugbot for commit 7255e97. Bugbot is set up for automated code reviews on this repo. Configure here.}

[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	Oct 5, 2026, 6:55 AM

[seidroid]

This change makes Importer.AddNode return an error. FlatKV now rejects non-leaf nodes, nodes without a key and nodes at the wrong version instead of skipping them, and snapshot restore stops on the first rejection so a rejected leaf never reaches the state store. Nothing blocks: the error path is wired through the composite and memiavl importers, the restore loop and the seidb tool, a failed import aborts and leaves the SS version unset, and tests cover it. I kept codex's one finding as a suggestion, because Close still returns the failure; no reading contributed anything else.

Non-blocking

1 finding on the changed lines, as inline comments.

_{seidroid review · decision approve · session 6145f229298746e986d8f5c2902d16c1 · turn resp_claude_e91be63b935713d88768a27f5f7988f9 · item bbe66940e7065ddbb2c04149420aafe2}

Findings: 0 blocking | 1 non-blocking | 1 posted inline

[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.69%. Comparing base (2740979) to head (1c3b5c6).

Files with missing lines	Patch %	Lines
...cmd/seidb/operations/import_flatkv_from_memiavl.go	75.00%	3 Missing ⚠️
sei-db/state_db/sc/composite/importer.go	50.00%	2 Missing ⚠️
sei-db/state_db/sc/flatkv/importer.go	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4412      +/-   ##
==========================================
- Coverage   55.70%   55.69%   -0.02%     
==========================================
  Files        2179     2179              
  Lines      169070   169090      +20     
==========================================
- Hits        94174    94167       -7     
- Misses      74891    74918      +27     
  Partials        5        5              

Flag	Coverage Δ
sei-chain	53.84% <80.00%> (-0.02%)	⬇️
sei-db	74.81% <ø> (ø)
sei-db-state-db	78.62% <86.95%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
sei-cosmos/storev2/rootmulti/store.go	75.29% <100.00%> (+0.07%)	⬆️
sei-db/state_db/sc/memiavl/import.go	75.95% <100.00%> (ø)
sei-db/state_db/sc/flatkv/importer.go	94.38% <94.11%> (-0.24%)	⬇️
sei-db/state_db/sc/composite/importer.go	90.24% <50.00%> (-4.76%)	⬇️
...cmd/seidb/operations/import_flatkv_from_memiavl.go	50.72% <75.00%> (+0.22%)	⬆️

... and 22 files with indirect coverage changes

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