Rename the telemetry tiers away from the borrowed control-plane/data-plane
jargon to plain language, across code, CLI output, config, and docs:
- "local plane" -> "local telemetry"
- "aggregate plane" -> "aggregate metrics"
- "trajectories plane" -> "trajectories" / "telemetry.trajectories"
- "three planes with a hard wall" -> "three settings, isolated from each other"
User-facing `hermes telemetry status` now reads "Local telemetry: on" /
"Aggregate metrics: off" / "Content export: off (trajectories disabled)".
The OTLP resource attribute key telemetry.plane is renamed to telemetry.scope
(wire-level identifier; nothing consumes it yet).
No behavior change — wording only. Status renders identically apart from the
labels; tests updated to match the new strings.