fix: Remove the BaseAccount inheritance from EvmServerAccount

[sddioulde]

Description

Removed the BaseAccount inheritance from EvmServerAccount.

Closes this issue.

Changes Made

1. Removed the problematic inheritance

• Changed class EvmServerAccount(BaseAccount, BaseModel) → class EvmServerAccount(BaseModel)
• Removed the runtime import of BaseAccount
• Kept BaseAccount as a TYPE_CHECKING-only import for type hints

2. Added comprehensive documentation

The new docstring explains:

• Why we don't inherit from BaseAccount (async vs sync incompatibility)
• How to get BaseAccount compatibility (use EvmLocalAccount wrapper)
• Code examples showing both the async pattern and the sync wrapper pattern

3. Fixed type annotations

• Added from __future__ import annotations for forward references
• Updated transfer() method signature to use proper type hints with BaseAccount

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Why This Works

1. No Breaking Changes in Practice

The code that would break (passing EvmServerAccount where BaseAccount is expected) was already broken because the methods return coroutines instead of results.

2. Existing Tests Pass

All tests pass because:

• Tests already use EvmLocalAccount (not EvmServerAccount) when a BaseAccount is needed
• Direct usage of EvmServerAccount with await continues to work unchanged

3. Clean Architecture

• EvmServerAccount = Pure async API (network-based operations)
• EvmLocalAccount = Sync wrapper for eth_account compatibility
• Users choose the right tool for their use case

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The Full Picture

This fix resolves the Liskov Substitution Principle violation mentioned in the GitHub issue. The class was claiming to be a BaseAccount but couldn't actually fulfill that contract because:

• BaseAccount methods are synchronous
• CDP API calls are inherently async (network operations)
• Making them "fake sync" with nested event loops is unreliable

The solution aligns with the codebase's existing pattern

• EvmLocalAccount already existed as the proper sync wrapper, so removing the false inheritance makes the architecture honest and clear.

Tests

Checklist

A couple of things to include in your PR for completeness:

• Updated the typescript README if relevant
• Updated the python README if relevant
• Added a changelog entry
• Added e2e tests if introducing new functionality

[cb-heimdall]

✅ Heimdall Review Status

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[0xRAG]

Overall LGTM, just had one question!