Telemetry docs mismatch and missing explicit opt-out controls

[pythrick]

I noticed a mismatch between the telemetry docs and the actual request, and I think we should tighten the user-facing controls.

Right now docs/telemetry.md says a background GET request is sent, but telemetry/telemetry.go sends a POST with JSON:

{"uuid":"...","version":"..."}

The code path is in telemetry.Ping().

Could we do a small cleanup pass:

• Update docs/telemetry.md to match the real request method/payload.
• Add an explicit opt-out in config (for example telemetry.enabled = false).
• Add a CLI override (--no-telemetry) for one-off runs.
• Show a one-time first-run note that telemetry is enabled and how to disable it.

I’m not arguing against telemetry here. Monthly anonymous MAU is reasonable. This is mostly about trust and making user control obvious.