Add Sandbox SDK on a unified httpx client (0.2.0)

[ats3v]

Adds the Sandboxes feature (deepinfra/backend#3148) and modernizes the package around one unified client.

What changed

• Sandbox API (sandbox_api.py): create (blocks until running, "10m"-style timeouts), from_id, list(tags=...), exec/run_python (aggregate the NDJSON exec stream), fs.read/fs.write, stop/start/terminate, context managers, and async twins (acreate, aexec, ...) for every network method. stop()/start() block until the state transition completes (wait=False to fire-and-forget) — stop/terminate are asynchronous server-side (~2s), so sb.stop(); sb.start() used to 409. wait_until_stopped/await_until_stopped are public alongside wait_until_running.
• One DeepInfraClient, rewritten in place onto httpx (was requests, single-URL, POST-only): sync + async, streaming, pooled connections, typed exceptions parsed from both {"error"} and FastAPI {"detail"} error shapes. Retries: connect-errors where marked, 502/503/504 only on GETs, never on non-idempotent POSTs (the old client retried 4xx ×5).
• Typed exception hierarchy under deepinfra/deepinfra.exceptions: 429 maps to RateLimitError (TooManySandboxesError kept as an alias), MaxRetriesExceededError is preserved as a subclass of APIConnectionError, and SandboxTimeoutError/SandboxFailedError carry .sandbox_id so a failed Sandbox.create(wait=True) still leaves a handle for cleanup.
• Legacy inference wrappers keep their public API (TextGeneration, Embeddings, AutomaticSpeechRecognition, TextToImage) but now run on the unified client; requests/requests-toolbelt dropped. Also fixes from deepinfra import TextGeneration, which was missing from the exports in 0.1.0.
• Packaging/CI: hatchling pyproject.toml (0.2.0, py>=3.9, deps httpx+pydantic only), py.typed, CI on GitHub-hosted runners with a 3.9–3.13 matrix (ruff, mypy, pytest), PyPI trusted publishing on v* tags with a tag==version guard, README/CHANGELOG/examples.

Not in this PR (designed, lands next)

exec_stream, snapshot/from_snapshot, expose_port, fs.upload_dir — no stubs shipped; each lands behind its backend endpoint. The server side of exec/fs is stubbed in deepinfra/backend#3474; end-to-end verification follows once the implementation PR lands.

Pre-publish audit round (2026-07-20)

A full review pass (core client, sandbox API, legacy wrappers, tests, packaging, docs) before the repo goes public. Fixed, each with regression tests:

• Constructing a legacy wrapper with no API key crashed with AttributeError instead of warning (refactor regression; the missing-key path had no test — now it does).
• parse_duration(0.5) silently truncated to 0 ("use server default"); fractional seconds now round up.
• 429 raised the sandbox-named TooManySandboxesError for inference rate limits too → RateLimitError introduced (alias kept).
• Wait-failure exceptions gained .sandbox_id (create-leak cleanup path).
• Coverage gaps closed: async retry loop (connect error / 502 / retries exhausted), ReadTimeout → APITimeoutError mapping, exec-stream heartbeats on the async path.
• Docs: the process-wide async client's pool binds to the first event loop — README/docstring note recommends a per-loop DeepInfraClient when calling asyncio.run() repeatedly. deepinfra/utils/ got its missing __init__.py.

Verification

Prod e2e (2026-07-20, real sandboxes against api.deepinfra.com): every deployed surface passes, sync + async — create (wait/no-wait), wait_until_running, refresh, list + tag filtering, from_id, stop(wait=True) → start() (previously 409ed), stop(wait=False) + wait_until_stopped, terminate, both context managers, 404 mapping on bogus ids, and all four inference wrappers on the new client (including multipart ASR). Verified server semantics now documented: stop/terminate take effect ~2s after the call returns; terminate is a soft delete (sandbox stays fetchable by id as "deleted" briefly, disappears from list immediately). exec/run_python/fs return 501 Not implemented yet from prod — SDK raises a clean typed error; e2e for those is gated on the backend deploy, and the 0.2.0 tag should wait for a green run of that suite.

Earlier prod e2e (2026-07-10): 24/24 lifecycle + break-attempt checks (path-traversal ids, empty id, junk/negative durations, unknown plan, non-string tags, instant wait-timeouts, double-stop), no sandboxes leaked. Break-testing found and fixed two bugs: sandbox ids are now URL-quoted in paths (from_id("../models") escaped to /v1/models; now a clean 404 + ValueError on empty id), and create(wait=False) populates fields with one GET instead of returning an empty-state handle. Legacy wrappers verified against live models (GLM-4.5-Air incl. full-URL endpoint form, gte-large, whisper-tiny.en file-path and raw-bytes multipart, sd3.5-medium); the 2024 response dataclasses crashed on fields the API has since added (request_id, words) — pre-existing 0.1.0 breakage, fixed with drift-tolerant parsing + regression test.

Unit suite: 107 passed (respx-mocked, exercising the real request path), on Python 3.9 (oldest supported); mypy strict + ruff clean; wheel build + twine check verified, py.typed and all subpackages ship.