Fix transient hardware control recovery

[olujicz]

Summary

• Automatically re-probe DDC capabilities after repeated write failures using a 1s/5s/30s backoff, restoring hardware controls when a transient failure clears.
• Preserve the current built-in display brightness when a live DisplayServices read fails during reconfiguration.
• Suppress built-in backlight writes for failed-read refresh cycles so persisted or default brightness cannot be pushed back to the panel.
• Add regression coverage for both recovery paths.

Root cause

Runtime DDC write failures permanently removed the affected VCP capability from the cached display state, with no recovery path short of toggling hardware control or reconnecting. Separately, a transient built-in brightness read failure selected persisted/default state and the subsequent refresh reapplied that fallback to the physical backlight.

Validation

• Full direct-distribution test suite (just test)
• App Store scheme build (just build-appstore)
• SwiftFormat check (just format-check)
• SwiftLint on all changed files
• Commit-hook sensitive-data scan