feat: add terminology schema example and improve schema-list command

This commit completes Phase 2 of schema evolution work and establishes
a new example demonstrating schema usage for terminology documents.

## New Features

### Terminology Validation Example (examples/terminology/)
- Complete example terminology document with proper structure
- JSON schema with MarkiTect extensions for validation
- Demonstrates schema usage beyond manpages (glossaries, lexicons)
- Validates term structure: Definition, Synonyms, Related Terms, Examples
- Includes content control and quality validation rules
- Full documentation with usage examples and best practices

### Schema Registration System
- Registered terminology schema in markitect database
- Created schema catalog (markitect/schemas/schema-catalog.yaml)
- Copied schema to official location (markitect/schemas/)
- Provides metadata, features, and usage info for all schemas

### Improved schema-list Command
- Now displays creation timestamps in default output
- Table format includes Created/Updated columns
- Cleaner timestamp formatting (removed microseconds)
- Better visibility into when schemas were added

## Files Changed

Added:
- examples/terminology/README.md - Complete documentation
- examples/terminology/terminology-example.md - Example glossary
- examples/terminology/terminology-schema.json - Validation schema
- markitect/schemas/terminology-schema.json - Registered schema
- markitect/schemas/schema-catalog.yaml - Schema registry

Modified:
- markitect/cli.py - Enhanced schema-list with timestamps
- TODO.md - Documented Phase 2 completion and new example

Moved:
- SCHEMA_EVOLUTION_WORKPLAN.md → todo/ directory

## Schema Features Demonstrated

- Heading hierarchy validation (H1 → H2 → H3)
- Term structure validation with required/optional fields
- Content quality metrics (word counts, readability targets)
- MarkiTect extensions (x-markitect-sections, x-markitect-content-control)
- Classification system (required/recommended/optional/discouraged/improper)

## Usage

```bash
# List schemas with timestamps
markitect schema-list

# Validate terminology document
markitect validate glossary.md --schema terminology-schema.json

# View in table format
markitect schema-list --format table
```

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

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

markitect/schemas/schema-catalog.yaml

@@ -0,0 +1,77 @@
+# MarkiTect Schema Catalog
+#
+# This catalog provides metadata about available schemas for markdown document validation.
+# Schemas can be referenced by name or loaded from their file path.
+
+version: "1.0"
+description: "Catalog of registered MarkiTect schemas for document validation"
+
+schemas:
+  - id: "markitect-metaschema"
+    name: "MarkiTect Metaschema"
+    file: "markitect-metaschema.json"
+    version: "1.0"
+    description: "Metaschema for validating MarkiTect schema extensions"
+    type: "metaschema"
+    usage: "Used internally to validate schema files with MarkiTect-specific extensions"
+    tags:
+      - internal
+      - validation
+      - metaschema
+
+  - id: "terminology-v1"
+    name: "Terminology Document Schema"
+    file: "terminology-schema.json"
+    version: "1.0"
+    description: "Schema for validating terminology and glossary documents"
+    type: "document-schema"
+    usage: "Validates technical glossaries, terminology documents, and definition lists"
+    document_types:
+      - glossary
+      - terminology
+      - lexicon
+      - dictionary
+    features:
+      - Heading hierarchy validation (H1 → H2 → H3)
+      - Term structure validation (Definition, Synonyms, Related Terms, etc.)
+      - Content quality metrics (word counts, readability)
+      - MarkiTect extensions (x-markitect-sections, x-markitect-content-control)
+      - Classification system (required/recommended/optional)
+    example: "examples/terminology/terminology-example.md"
+    tags:
+      - documentation
+      - glossary
+      - terminology
+      - definitions
+    related_schemas: []
+    author: "MarkiTect Project"
+    created: "2026-01-04"
+    updated: "2026-01-04"
+
+# Future schemas to add:
+#
+# - id: "manpage-v1"
+#   name: "Unix Manual Page Schema"
+#   description: "Schema for Unix/Linux manual page documentation"
+#
+# - id: "api-reference-v1"
+#   name: "API Reference Schema"
+#   description: "Schema for API endpoint documentation"
+#
+# - id: "arc42-v1"
+#   name: "arc42 Architecture Documentation Schema"
+#   description: "Schema for arc42 architecture documentation template"
+#
+# - id: "adr-v1"
+#   name: "Architecture Decision Record Schema"
+#   description: "Schema for ADR (Architecture Decision Record) documents"
+#
+# - id: "rfc-v1"
+#   name: "RFC/Specification Schema"
+#   description: "Schema for RFC-style specification documents"
+
+# Schema discovery paths:
+# - Built-in: markitect/schemas/*.json
+# - User-defined: ~/.markitect/schemas/*.json
+# - Project-specific: .markitect/schemas/*.json
+# - Custom paths via MARKITECT_SCHEMA_PATH environment variable