chore: archive completed schema-of-schemas implementation

Moved schema-of-schemas planning artifacts from roadmap to history
with datestamp prefix, marking completion of all 6 implementation phases.

**Changes:**
- Moved roadmap/schema-of-schemas/ → history/2026-01-05-schema-of-schemas/
- Updated all documentation references to new location
- Marked implementation as completed in TODO.md
- Updated CHANGELOG.md to reflect archived status

**Implementation Summary:**
All 6 phases completed successfully:
- Phase 1: Filename validation (50 tests)
- Phase 2: Markdown schema loader (35 tests)
- Phase 3: Schema-for-schemas metaschema (12 tests)
- Phase 4: Schema migration (2 migrated, 3 deleted)
- Phase 5: CLI enhancements (multi-schema validation)
- Phase 6: Integration testing and documentation

**Deliverables:**
- 97 unit tests (100% passing)
- 4 production schemas in registry
- Comprehensive user documentation
- Updated examples (manpages, terminology)
- Complete schema management system

The schema-of-schemas topic is now complete and archived for
historical reference.

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

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

CHANGELOG.md

@@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Markdown-first schema format with embedded JSON (documentation + schema in one file)
   - Schema catalog (`markitect/schemas/schema-catalog.yaml`) for metadata and discovery
   - Terminology validation example (`examples/terminology/`) demonstrating schema usage beyond manpages
-  - Schema-for-schemas workplan in `roadmap/schema-of-schemas/` directory
+  - Schema-of-schemas implementation archived in `history/2026-01-05-schema-of-schemas/`
 - **Enhanced schema-list Command**: Now displays numbered references in all output formats for easy selection
   - Simple format: `[1] schema-name.md` prefix for each schema
   - Table format: `#` column as first column
@@ -34,9 +34,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Enhanced control panel UI with better resize handle positioning for improved user interaction
 
 ### Changed
-- **Directory Reorganization**: Renamed `todo/` → `roadmap/` for better organization of planning documents
-  - Created `roadmap/schema-of-schemas/` subdirectory for schema management planning artifacts
-  - Moved schema management proposals and workplan to dedicated directory
+- **Directory Reorganization**:
+  - Renamed `todo/` → `roadmap/` for better organization of planning documents
+  - Completed schema-of-schemas implementation archived to `history/2026-01-05-schema-of-schemas/`
+  - Moved completed planning artifacts to history for reference
 - Refactored contents control architecture to use base class pattern properly for better code organization
 - Updated all file references and paths to point to single source of truth in capabilities/testdrive-jsui/js/controls/ directory