Fix stale import fixer status

[predict-woo]

Summary

• wait for the cancelled import progress consumer to terminate
• commit the final idle or failed UI state only after queued progress updates are drained
• prevent a late fixing event from restoring the completed import indicator

Closes #4.

Verification

• swift format lint passed
• Swift package build passed
• all 309 package tests passed
• Xcode Debug build passed
• launched the newly built app and verified the note UI