Verification Checklist

Test with a drawing that has no active scale, a drawing with a known scale, and a reference length suitable for calibration.

• Header, ribbon, sidebar toggle, active-scale card, and Canvas workspace remain usable at desktop and mobile sizes.
• Opening clears the previous active file index; opening, opened, failed, and fileInfo update host state through documented NPM events.
• Ribbon measurement actions stay disabled until a snapshot confirms an active scale.
• Tool activation awaits viewer.tools.set({ action, enabled: true }) and only marks the tool active when result.success is true.
• The Calibrate tab shows Start, Cancel, picked length, Calculate, candidate, and Apply only in their valid states.
• The floating picking banner appears while calibration is active and disappears after finished or cancel.
• Metric and Imperial calibration fields use the documented correction field names and validation rules.
• Calculator presets create a complete scale with isSelected: true and wait for snapshot confirmation.
• Scale library rows use full known scale data; deletion affects host-only custom presets, never undocumented Canvas scale deletion.
• Apply uses viewer.measurements.calibration.apply({ requestId, fileIndex }) and tools remain gated until its snapshot confirms an active scale.
• Document presets, scale-library rows, tabs, and cancellation are keyboard and screen-reader operable.
• File change, cancel, timeout, and unmount clear request-specific state and listeners.