docs: record v0-m9-done tag

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/PROGRESS.md

@@ -196,7 +196,7 @@ Validation:
 - Code signing is ad hoc only (no purchased Apple Developer ID or Windows code-signing certificate), so macOS Gatekeeper and Windows SmartScreen still show first-run warnings by design
 
 Git:
-- Tag: Pending user approval
+- Tag: `v0-m9-done`
 
 ## Milestone 10 - v1.0 Stabilization