Add RTM2000 transactional scope focus

[Scaxlibur]

Summary

• implement complete RTM2000 focus snapshot, configure, and restoration methods for CH1/CH2
• promote scope.focus_configure_v2 in the production descriptor
• move RTM-specific channel topology, numeric request guards, tolerances, and I/O budgets into the plugin profile
• release the capability as plugin 0.15.0 with WaveBench 0.8.26 as the minimum Core version
• preserve the fixed restoration order: timebase, channel vertical state, then channel display

The profile bounds are WaveBench plugin request guards. They are not a claim that every boundary value was exercised point by point on hardware.

Hardware acceptance

RTM2032 firmware 06.010 was used as the representative RTM2000-series hardware baseline. Per-model repetition is not required for this family capability.

• DG4202 CH1/CH2 outputs stayed OFF; scope inputs were DCL high impedance and not overloaded
• initial view: 5 ms, CH1/CH2 both ON, both 0.2 V/div, position and offset zero
• target view: 10 ms, CH2 0.4 V/div, CH1 hidden
• target and restored views both passed fresh readback
• 6/6 text writes completed, with zero unknown outcomes and zero binary writes
• a new read-only session independently confirmed restoration to the complete initial view

Live communication failures were not manufactured. Partial-write, postcondition-mismatch, restoration-failure, and poisoned-session paths remain covered by controlled offline fault injection.

Validation

• RTM package: 197 passed
• full plugin repository: 1860 passed, 3 skipped
• Ruff, pip check, editable environment check, descriptor doctor, documentation rules, and git diff --check passed
• plugin package check: version 0.15.0, status valid, SHA-256 ae39a383152110695aca1bfea3dbef50129b3d4933c0b212ffcc639d52b5096a

Stack

This PR is stacked on plugin PR #9 and depends on Core PR Scaxlibur/WaveBench#16. After the parent PRs merge, this PR can be retargeted to main.

MSO8000 and SDS3000 focus capabilities remain production-disabled.