## Why

Gateway heartbeat currently carries active sessions and one egress rate but cannot transport the required observed process and provider-path telemetry.

## What Changes

- Add one required bounded low-cardinality telemetry object to authenticated gateway heartbeat.
- Cover counters, delay totals/samples, control RTT/loss/jitter, pending reliability, reconnects, and provider state.
- Keep configured capacity exclusively in registration and measured egress in heartbeat.

## Capabilities

### New Capabilities

- `gateway-heartbeat-telemetry`: Authenticated heartbeats carry bounded observed gateway telemetry without routes, sessions, credentials, or payload data.

### Modified Capabilities

None.

## Impact

The control-v1 schema, generated Go/Rust/Swift bindings, conformance checks, and both unpublished consumers require coordinated local updates. RC6 remains unchanged.