Update Docs/StreamHub-API.md (new setCalibration/reloadConfig commands,
calibration/configSaved/configReloaded events, §4 config file format),
ARCHITECTURE.md §6 (updated command/event tables and Config File Format
subsection), Docs/WebUI.md (Cal row in V-Scale Toolbar, Sources & Config
sidebar section). Also corrects the spec's Validation sentence to match
the shipped cal-invalid border behaviour instead of silent field revert.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
