migration routers

[cody-littley]

Describe your changes and provide context

Use the migration router primitives to construct the migration workflows we will need.

Use the following link to view the README in rendered form. Suggested read prior to reviewing code. https://github.com/sei-protocol/sei-chain/blob/cjl/migration-integration/sei-db/state_db/sc/migration/README.md

Testing performed to validate your change

unit tests

[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	May 5, 2026, 3:38 PM

[codecov]

Codecov Report

❌ Patch coverage is 55.32995% with 176 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.09%. Comparing base (ab2b373) to head (2f50f90).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-db/state_db/sc/migration/router_builder.go	58.45%	47 Missing and 39 partials ⚠️
sei-db/common/testutil/test_random.go	16.66%	73 Missing and 2 partials ⚠️
sei-db/state_db/sc/migration/write_mode.go	0.00%	11 Missing ⚠️
sei-db/state_db/sc/migration/migration_manager.go	88.23%	1 Missing and 1 partial ⚠️
sei-db/state_db/sc/migration/router_kvstore.go	95.23%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3336    +/-   ##
========================================
  Coverage   59.08%   59.09%            
========================================
  Files        2099     2104     +5     
  Lines      172988   173358   +370     
========================================
+ Hits       102212   102443   +231     
- Misses      61911    61997    +86     
- Partials     8865     8918    +53     

Flag	Coverage Δ
sei-chain-pr	74.68% <55.32%> (?)
sei-db	70.41% <ø> (-0.22%)	⬇️

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

Files with missing lines	Coverage Δ
sei-db/state_db/sc/memiavl/store.go	93.02% <100.00%> (+0.43%)	⬆️
sei-db/state_db/sc/migration/module_router.go	100.00% <100.00%> (ø)
sei-db/state_db/sc/migration/store_keys.go	100.00% <100.00%> (ø)
sei-db/state_db/sc/migration/migration_manager.go	94.41% <88.23%> (-1.84%)	⬇️
sei-db/state_db/sc/migration/router_kvstore.go	95.23% <95.23%> (ø)
sei-db/state_db/sc/migration/write_mode.go	0.00% <0.00%> (ø)
sei-db/common/testutil/test_random.go	16.66% <16.66%> (ø)
sei-db/state_db/sc/migration/router_builder.go	58.45% <58.45%> (ø)

... and 37 files with indirect coverage changes

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