Implement Transaction Builder Wrapper

[wheval]

Implement Transaction Builder Wrapper

Description:
Build AccountTransactionBuilder — a convenience wrapper around Stellar SDK's TransactionBuilder that simplifies building smart account operations (session key management, contract execution).

Context:
Invoking our account contract methods requires verbose Soroban invocation code. This wrapper provides a clean fluent API for common operations while delegating to Stellar SDK internally.

Requirements:

• Create AccountTransactionBuilder class wrapping Stellar SDK's TransactionBuilder
• Implement .addSessionKey(publicKey, permissions, expiresAt) convenience method
• Implement .revokeSessionKey(publicKey) convenience method
• Implement .execute(sessionKey, operations) convenience method
• Implement .simulate() for Soroban transaction simulation
• Support .addOperation() passthrough for standard Stellar operations
• Automatic fee estimation from simulation results
• Implement .build() returning a ready-to-sign transaction
• Unit tests for all builder methods (>90% coverage)

Files to Create:

• packages/account-abstraction/src/transaction-builder.ts
• packages/account-abstraction/src/__tests__/transaction-builder.test.ts

Dependencies:

• @stellar/stellar-sdk
• @ancore/types
• @ancore/stellar
• Issue feat(account-abstraction): implement AccountContract SDK package #36 (account abstraction SDK)

Definition of Done:

• Builder produces valid Soroban transactions
• Simulation works and returns estimated fees
• All methods chain correctly (fluent API)
• Tests pass with >90% coverage

Labels: sdk, transactions, account-abstraction
Estimated Effort: 3–4 days
Priority: High — needed for send flow and session key management

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[Ogechizzzy]

@Ogechizzzy has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Please, I'd like to take on this issue, kindly assign it to me.

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