Full-Featured Python SDK (Sync + Async), Go Client SDK (pkg/client), and cubepod CLI (cmd/cubepod)

Source: docs/enhancements/0013-sdk-and-cli-completeness/README.md · Status: implemented · Area: core · Milestone: v0.3.0

1. Summary

Upgrades the CubePod client ecosystem to production completeness across both Python and Go:

Python SDK (sdks/python/cubepod):
- Adds CubePod (SyncCubePod) synchronous client alongside AsyncCubePod.
- Adds list_files(sandbox_id, path), delete_file(sandbox_id, path), get_command_status(sandbox_id, cmd_id), stream_command(sandbox_id, cmd_id) (SSE generator), create_warmpool(...), list_warmpools(), and list_templates().
- Adds transient HTTP retry/backoff (max_retries=2 on 502/503/504) and high-level AsyncSandboxSession / SandboxSession context managers (async with client.session(...) as sb:).
Go Client SDK (pkg/client/client.go):
- Idiomatic, zero-external-dependency Go client covering all Sandbox, Command, File (WriteFile, ReadFile, DeleteFile, ListFiles, ArchiveSync, ArchiveSyncDir), Panel Token, and WarmPool APIs.
cubepod CLI (cmd/cubepod/main.go):
- First-class CLI tool (bin/cubepod) for developers and CI pipelines (cubepod sandbox create|list|get|exec|write-file|read-file|ls|rm|archive-sync|pause|connect|reset-rootfs|fork|delete, cubepod warmpool create|list, cubepod health).

Provide both async and sync Python ergonomics so any Python agent framework (LangGraph, CrewAI, AutoGen, CubePlex) can integrate without event-loop friction.
Provide a native Go SDK (pkg/client) and cubepod CLI binary (bin/cubepod) for Go services, Kubernetes E2E tests, and terminal workflows.

AsyncCubePod additions:
- list_files(sandbox_id: str, path: str = "/workspace") -> list[FileEntry]
- delete_file(sandbox_id: str, path: str) -> str
- get_command_status(sandbox_id: str, command_id: str) -> CommandInfo
- stream_command(sandbox_id: str, command_id: str) -> AsyncIterator[CommandLogs]
- create_warmpool(name: str, template_id: str, replicas: int = 2) -> dict[str, Any]
- list_warmpools() -> list[dict[str, Any]]
CubePod (SyncCubePod):
- Uses httpx.Client with identical method signatures (synchronous) and with CubePod(...) as client:.

type Client struct { baseURL string; apiKey string; httpClient *http.Client }
Methods: Health, CreateSandbox, GetSandbox, ListSandboxes, DeleteSandbox, PauseSandbox, ConnectSandbox, ResetRootFS, ForkSandbox, SetTimeout, AcquireLease, RunCommand, GetCommandStatus, GetCommandLogs, KillCommand, WriteFile, ReadFile, DeleteFile, ListFiles, ArchiveSync, GetPanelEndpoint, CreateWarmPool, ListWarmPools.

Uses --gateway-url (or CUBEPOD_GATEWAY_URL, default http://127.0.0.1:8080) and outputs clean JSON or human-readable output.

Unit tests in sdks/python/tests/test_sdk.py testing both AsyncCubePod and CubePod (SyncCubePod), including list_files, delete_file, get_command_status, warmpools, and retry handling.
Unit tests in pkg/client/client_test.go testing all Go SDK methods against httptest.Server.

Code-generated OpenAPI clients: Hand-crafted httpx and net/http clients have zero bloat, zero external codegen dependencies, and first-class streaming/tar.gz helpers.