Giga fixes

[stevenlanders]

Describe your changes and provide context

This PR introduces three critical fixes to align the Giga executor with V2 behavior and resolve apphash mismatches:

1. Initial Fee Validation: Implements upfront fee validation (fee cap, tip cap, overflow, gas limit) before EVM execution, mirroring V2's ante handler. This fix ensures the nonce is correctly incremented even when validation fails.
2. Return All Balances: Updates the bank keeper's SpendableCoins() to return all token balances, not just usei, addressing an apphash mismatch and enabling multi-token support.
3. Nonce Increment on Early Exit: Ensures the transaction nonce is incremented even when transactions fail validation early, preventing nonce desynchronization and further apphash mismatches.

These changes are crucial for maintaining consensus and state parity between Giga and V2 execution paths.

Testing performed to validate your change

This PR is intended to be merged into staging-feb13/giga-6.3.0 for comprehensive testing. Further unit, integration, and regression tests are recommended, especially for validation failure paths and the specific transactions that triggered the apphash mismatches.

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Feb 11, 2026, 9:43 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.11%. Comparing base (7db2f0a) to head (89344e9).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2863       +/-   ##
===========================================
+ Coverage   48.32%   57.11%    +8.78%     
===========================================
  Files         671     2090     +1419     
  Lines       50576   171169   +120593     
===========================================
+ Hits        24439    97755    +73316     
- Misses      23998    64720    +40722     
- Partials     2139     8694     +6555     

Flag	Coverage Δ
sei-chain	52.56% <ø> (?)
sei-cosmos	48.13% <ø> (-0.01%)	⬇️
sei-db	68.72% <ø> (ø)

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