Refactor eth tx nonce subsystem and enforce linear growth

[libotony]

Summary

Builds on eth-equivalence (which already has on-state nonce wiring from #1616 with two changes:

Refactor

• state.Account.Nonce: []uint64 with rlp:"tail" → uint64 with rlp:"optional" (same byte-encoding, simpler in-memory shape).
• runtime/statedb: struct-with-txType-field → StateDB interface with V1 (no-op SetNonce) and V2 (write-through SetNonce). Dispatched by txCtx.Type in Runtime.newStateDB.
• Nonce CALL-path inc moved from PrepareTransaction (post-clause) to PrepareClause (pre-evm.Call). Mirrors Ethereum's nonce-write-outside-EVM-snapshot pattern; on VMErr, eth tx skips the outer state.RevertTo so the increment survives.

Add

• Linear nonce growth enforcement across txpool / packer / consensus. < reject, > queue/defer/invalid, == admit.
• End-to-end eth tx execution tests (transfer / creation / revert preserves nonce / sponsored / fee floor / insufficient balance).
• Multi-clause revert regression test.
• Cross-coverage with evm-upgrades EIPs (7825 gas cap, 1153 transient storage isolation, 6780 same-tx + pre-existing selfdestruct)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• New and existing E2E tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 58.06452% with 26 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
consensus/validator.go	28.57%	8 Missing and 2 partials ⚠️
packer/flow.go	50.00%	2 Missing and 2 partials ⚠️
state/state.go	66.66%	2 Missing and 2 partials ⚠️
txpool/tx_object.go	50.00%	2 Missing and 2 partials ⚠️
runtime/runtime.go	80.00%	1 Missing and 1 partial ⚠️
vm/evm.go	0.00%	1 Missing and 1 partial ⚠️

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