feat(prompts): implement Phase 2 - Templates & Macros (FR-2)

Implement PromptTemplate models with ContentMacro parsing and analysis.

Core Features:
- PromptTemplate extending Artifact for template-specific operations
- ContentMacro model supporting REQUIRED, OPTIONAL, GENERATE kinds
- MacroParser for extracting macros from template content
- TemplateAnalyzer for dependency extraction and validation
- TemplateService for high-level template operations
- Template metadata for model hints and expected inputs

Macro Syntax:
- {{require:artifact-name}} - Required dependency
- {{optional:artifact-name}} - Optional dependency
- {{generate:template-name|param=value}} - Nested generation

Tests (38 passing):
- 18 template model tests (macros, templates, metadata)
- 20 parser tests (parsing, validation, parameters, aliases)

Implements:
- FR-2.1: PromptTemplate as content artifact with macros
- FR-2.2: ContentMacro detection and extraction
- FR-2.3: Required/Optional/Generate macro kinds

Files Created:
- markitect/prompts/templates/models.py
- markitect/prompts/templates/parser.py
- markitect/prompts/templates/analyzer.py
- markitect/prompts/services/template_service.py
- tests/unit/prompts/test_template_models.py
- tests/unit/prompts/test_macro_parser.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

markitect/prompts/templates/__init__.py

@@ -0,0 +1,24 @@
+"""
+Template and macro management for Prompt Dependency Resolution.
+
+This package provides PromptTemplate definitions, macro parsing,
+and template analysis for dependency extraction.
+"""
+
+from markitect.prompts.templates.models import (
+    PromptTemplate,
+    ContentMacro,
+    MacroKind,
+    TemplateMetadata,
+)
+from markitect.prompts.templates.parser import MacroParser
+from markitect.prompts.templates.analyzer import TemplateAnalyzer
+
+__all__ = [
+    "PromptTemplate",
+    "ContentMacro",
+    "MacroKind",
+    "TemplateMetadata",
+    "MacroParser",
+    "TemplateAnalyzer",
+]