Throw descriptive error when sandbox is killed mid-request

[mishushakov]

When the sandbox is killed or times out while a request is in flight, runCode/run_code and the context-management methods surfaced a raw socket error (e.g. ECONNRESET on Bun, TypeError: fetch failed on Node, httpx.ReadError/RemoteProtocolError in Python). Both SDKs now detect the closed connection across runtimes, confirm via the sandbox health check that it's actually gone, and throw a descriptive SandboxError/SandboxException suggesting timeoutMs/.setTimeout instead. If the sandbox is still running or its state can't be determined, the original error propagates unchanged so genuine network issues aren't masked. Includes kill-during-execution tests for JS, Python sync, and Python async (verified against the live API on Node and Bun), plus a patch changeset for both packages.

🤖 Generated with Claude Code

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PR Summary

Low Risk
Narrow change to error mapping on existing request paths; real network blips stay as original errors when the sandbox still appears running or state cannot be checked.

Overview
When a sandbox dies or times out during runCode/run_code or context API calls, clients used to surface low-level connection failures (ECONNRESET, fetch TypeError, httpx.ReadError/RemoteProtocolError). Both JS and Python now treat those as possible mid-flight kills, confirm with isRunning() (and leave the original error if the check fails or the sandbox is still up), then raise a TimeoutError/TimeoutException that explains the sandbox was killed and points at timeout options.

JS adds isConnectionClosedError for runtime-specific socket-reset shapes and routes request failures through handleRequestError instead of only formatRequestTimeoutError. Python adds format_sandbox_killed_error and _handle_connection_error on the same code paths. Integration tests kill the sandbox during a long sleep for JS, sync Python, and async Python; a patch changeset covers both packages.

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