Add optional OpenTelemetry tracing hooks to the Python SDK

Motivation

OpenShell users need visibility into remote execution latency, failures, and gateway interactions. Optional OpenTelemetry hooks would improve observability without forcing tracing dependencies into the core install.

Proposed change

Auto-detect OpenTelemetry when installed and emit spans around major Python SDK operations such as connection setup, execution calls, and teardown. The implementation should be no-op when OpenTelemetry is not installed or not configured.

Acceptance criteria

• Do not add a hard dependency on OpenTelemetry in the core package.
• Emit spans for major SDK operations with useful attributes such as operation name, gateway target, status, and error type.
• Add tests using a mocked or in-memory tracer provider.
• Document how to enable tracing.

Notes

This is intended as an SDK-only change.

No files or tests are named. Start by locating the Python SDK's connection setup, execution, and teardown entry points, then review how optional dependencies are handled. Done means optional tracing emits useful spans without a core OpenTelemetry dependency, tests cover a mocked or in-memory tracer, and enablement is documented.