chore: remove dead agentops trace init CLI command #91

Summary

Removed the agentops trace init CLI stub that was never implemented and confused users into thinking tracing required manual setup.

What was done

• Removed trace_app Typer sub-app from cli/app.py
• Removed app.add_typer(trace_app) registration
• Removed cmd_trace_init() handler
• Removed test_trace_init_is_planned_stub from tests/unit/test_cli_commands.py

Why

Tracing is now built-in — it activates automatically when AGENTOPS_OTLP_ENDPOINT is set. A manual trace init command is misleading.

Implemented in

PR #86 (feature/telemetry-doc -> develop)