docs: update PRD with Section 9 progress (Phases 1-2 complete)

Section 9 (Unit Testing) status updated:
- Phase 1: Test infrastructure & model tests (29 tests) ✓
- Phase 2: Configuration & field mapping tests (44 tests) ✓
- Total: 73 passing tests, ~40% estimated coverage

Remaining phases (3-5) planned for future work to reach 70% target.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: leogdion

.claude/PRD.md

@@ -12,7 +12,7 @@
 - ✅ **Section 6**: XcodeGen Integration - COMPLETED (project.yml configuration)
 - ✅ **Section 7**: Documentation - COMPLETED (DocC catalog, organized markdown docs)
 - ✅ **Section 8**: README Improvements - COMPLETED
-- ⏳ **Section 9**: Unit Testing - Not started
+- ⏳ **Section 9**: Unit Testing - In Progress (Phases 1-2 complete: 73 tests, ~40% coverage)
 - ⏳ **Section 10**: BushelKit Integration - Not started
 - ⏳ **Section 11**: Project Configuration - Not started
 - ⏳ **Section 12**: Release Preparation - Not started