refactor state DB / snapshot interfaces

[cody-littley]

Describe your changes and provide context

Rename "snapshots" to "views", other minor refactors

[cursor]

PR Summary

Low Risk
Interface-only changes in the giga state DB layer with no implementations or production callers in this diff; breaking API renames for future integrators.

Overview
Refactors the giga state DB API by moving the top-level StateDB interface into a new state_db.go file and renaming read surfaces from snapshot to view terminology (StateSnapshot → StateView, EVMStateSnapshot → EVMStateView, OpenSnapshot / OpenSnapshotAt → OpenView / OpenViewAt).

The read-only StateView.Get signature now takes a module string plus key (Get(module string, key []byte)), so raw KV reads are scoped by module instead of a single global key space. Comments and lifecycle wording are updated to match “view” naming (e.g. reads do not observe writes after the view was opened).

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[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	Aug 27, 2026, 8:39 PM

[seidroid]

Pure rename/reorganization of the declaration-only giga package: StateSnapshot/EVMStateSnapshot/OpenSnapshot* become StateView/EVMStateView/OpenView*, and StateDB moves to its own file with the proto import. No implementations or callers exist in the tree, so nothing breaks, and doc comments were updated consistently.

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

Blockers

• None at the file/PR level.

Non-blocking

• None at the file/PR level.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.24%. Comparing base (991d64c) to head (ac2420a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4041      +/-   ##
==========================================
- Coverage   61.23%   60.24%   -0.99%     
==========================================
  Files        2153     2054      -99     
  Lines      188412   176727   -11685     
==========================================
- Hits       115381   106476    -8905     
+ Misses      62285    60472    -1813     
+ Partials    10746     9779     -967     

Flag	Coverage Δ
sei-db	69.80% <ø> (ø)
sei-db-state-db	?

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