v0.9.0 — Notifications and Polish

[danielithomas]

Summary

Desktop notifications on status transitions and CLI polish.

Key deliverables

• Desktop notifications via notify-send / gi.repository.Notify (daemon fires these)
• Configurable thresholds per provider
• --notify flag
• Shell completion scripts (bash, zsh, fish)
• Man page
• Tests for notification logic
• README update with notifications documentation

See docs/SPEC.md Section 14, v0.9.0 for full checklist.