Studio: Debug ▾ telemetry ring toggle doesn't show whether it's on or off #277

Problem

The Debug ▾ → Health → "Telemetry ring: on/off" item in the Arena Studio Console is a blind toggle. The label always reads "on/off", so you can't tell the current state from the menu. Clicking it flips a remembered per-browser setting (localStorage studio_telemetry). The only feedback is one Console log line (telemetry ring ENABLED|DISABLED (remembered)).

Found during QC of #274 on reiserlab-ww18 (2026-10-27): the ring had been switched off in that browser at some point and stayed off. Run 1 was logged with run_metadata.telemetry: "off", so runlog-check failed (no stream_schema, no trial_quality, cc_0x70_ok: 0). Nothing in the menu showed it. The state is also more than on/off: the ring only runs if the setting is on, the firmware advertises it (GET_FIRMWARE_VERSION flags bit 2), and SET_TELEMETRY was acked. Today only the Console log line telemetry ring: poller stopped (<why>) says which one failed.

Proposal

• Show the state in the item itself, the way other Studio toggles do: text plus aria-pressed (or role="menuitemcheckbox" + aria-checked). For example "Telemetry ring: On" / "Off".
• Show the effective state next to it when connected: draining 10 Hz · off (setting) · unavailable (firmware has no ring) · refused (SET_TELEMETRY). That's Studio.telemetryEnabled() + Studio.telemetryAvailable + the stopTelemetry reason.
• Optional: show a small indicator outside the Debug menu when telemetry is off on a firmware that supports it, since it changes what the run log contains. For example the device line, or the Run view before Run experiment.
• Keep the engineer title= tooltip and the HELP map text ([data-cmd="ctelem"]) in step with the new label.

Code: arena_studio.html, the data-cmd="ctelem" button, the ctelem handler, and Studio.telemetryEnabled / setTelemetryEnabled / initTelemetry.

Done when

• You can read on/off from the Debug menu without clicking.
• When connected, the item says whether the ring is actually draining, and if not, why.
• tests/test-studio-shell.js / pixi run studio-smoke still pass.