Previously modals showed generic "Failed to add/save" messages. Now they
extract and display the actual error detail from the API response (e.g.,
"URL is required", "Name already exists"). Handles Pydantic validation
arrays by joining msg fields.
Fixed in 8 files: device-discovery, devices, calibration,
advanced-calibration, scene-presets, automations, command-palette.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
alexei.dolgolyov
f4647027d2