Add typed scope channel display control

[Scaxlibur]

Summary

• add the typed scope.channel_display_configure_v2 request/state/profile/protocol surface
• execute channel display changes through the current operation-spec and service transaction model
• suppress no-op writes, verify postconditions, and restore/verify the baseline after failures
• add wavebench scope display --channel N on|off
• keep support optional and profile-gated; Core built-in descriptors are not promoted by this PR

Relationship to #3

This supersedes the channel-display portion of #3 using the current typed plugin architecture.

It intentionally does not implement scope focus, time-range/vertical-scale changes, or hide-other-channels. Those remain a separate follow-up because they require a wider multi-field baseline and restore transaction. Profiles may expose multiple channels, but each display operation changes exactly one selected channel.

Validation

• focused scope display suite: 46 passed
• full Core suite: 2092 passed, 1 skipped, 131 subtests passed
• Ruff: passed
• documentation lint: passed
• git diff --check: passed

Merge/release note

The matching plugin work targets the existing Core development version 0.8.25. No 0.8.25 release artifact currently exists; plugin promotion/release should follow this Core change.