[Feature]: add context edit method

[gusye1234]

Describe the solution you'd like

Implement context edit feature: https://platform.claude.com/docs/en/build-with-claude/context-editing
support clear_tool_use strategy.

Use Case

Reduce the current session tokens to enable long-running agents.

Proposed API/Interface

client.sessions.context_edit(session_id='xxxx', strategy="clear_tool_use")

Component/Area

Which part of Acontext would this feature affect?

• Client SDK (Python)
• Client SDK (TypeScript)
• Core Service (Python)
• API Server (Go)
• UI/Dashboard (Next.js)
• CLI Tool
• Documentation
• Other (please specify)