[W5][SDK][M] Add strongly typed error taxonomy for SDK transaction helpers

[kike-alt]

ID: W5-3C-SDK-001
Track: SDK
Phase: 3C
Difficulty: intermediate
Priority: P1

Description

Create consistent SDK error classes/enums for simulation, submission, and decode failures.

Acceptance Criteria

• Define implementation plan aligned to scope boundaries
• Implement and verify changes in soroban/sdk/ts/tx-builder.ts
• Implement and verify changes in soroban/sdk/ts/types.ts
• Add/adjust tests or validation artifacts for the changed surface
• Update docs/notes if behavior or operations change

Relevant Files/Modules

• soroban/sdk/ts/tx-builder.ts
• soroban/sdk/ts/types.ts

Dependencies / Blocked By

• [W5][SDK][M] Add transaction lifecycle helper primitives for simulate/submit/poll #584

Validation Requirements

• frontend/backend consumers compile using typed error handling