feat(sdk/python): add async PoolManager and PoolsAdapter

[wangdengshan]

Summary

• Add async PoolManager and PoolsAdapter to the Python SDK for managing pre-warmed sandbox pools
• Add domain models: PoolCapacitySpec, PoolStatus, PoolInfo, PoolListResponse, CreatePoolParams, UpdatePoolParams
• Add Pools Protocol (async service interface)
• Add attrs-style API lifecycle models for all pool schemas
• Add 5 API modules (post/get/list/put/delete) with both asyncio_detailed and sync_detailed functions
• Add PoolsAdapter (async HTTP adapter using httpx.AsyncClient)
• Add PoolManager with static create(), CRUD methods, and async context manager (__aenter__/__aexit__)
• Export PoolManager from opensandbox root __init__

Testing

• Unit tests
• 41 tests covering models, adapter mapping, and manager logic

Breaking Changes

• None

Checklist

• Linked Issue or clearly described motivation
• Added/updated docs (if needed)
• Added/updated tests (if needed)
• Security impact considered
• Backward compatibility considered

[github-actions]

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Changed directories: sdks.

📋 Recommended labels (based on changed files):

• sdks ⬅️

Other available labels:

• bug - Something isn't working
• dependencies - Pull requests that update a dependency file
• documentation - Improvements or additions to documentation
• feature - New feature or request
• packages - Changes for package, image and configuration

💡 Tip: Use feature for new functionality or improvements, bug for fixes.

cc @wangdengshan

[wangdengshan]

Hi maintainers, could someone please add the sdks and feature labels to this PR? As an external contributor I do not have permission to add labels myself. Thanks!