feat(spaces): implement Phase 0-1 of Information Space Service

Phase 0 - Project Organization:
- Create docs/PROJECT_STRUCTURE.md documenting codebase layout
- Create markitect/core/ with parser, serializer, document_manager, workspace
- Create markitect/schema/ consolidating 6 schema_*.py modules
- Create markitect/storage/ with database module
- Maintain backward compatibility via re-exports from original locations
- Add docs/roadmap/information-space-service/ with README and WORKPLAN

Phase 1 - Foundation (Weeks 1-3):
- Week 1: Core domain models (InformationSpace, SpaceDocument, SpaceConfig,
  SpaceMetadata, SpaceVariable, TransclusionReference, SpaceStatus)
- Week 2: Repository layer with interfaces (ISpaceRepository,
  IDocumentAssociationRepository, IVariableRepository, IReferenceRepository)
  and SQLite implementations with foreign key cascade deletes
- Week 3: SpaceService orchestration layer with full CRUD, document,
  variable, and reference tracking operations

Test coverage: 124 tests (25 model + 63 repository + 36 integration)

Capabilities delivered:
- CAP-001: InformationSpace entity with lifecycle management
- CAP-002: SpaceRepository CRUD with SQLite backing
- CAP-003: Document-Space associations with path-based organization
- CAP-004: Space metadata and configuration schemas
- CAP-005: Database schema with migrations

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

markitect/parser.py

@@ -1,26 +1,11 @@
-from markdown_it import MarkdownIt
+"""
+Markdown AST Parser - Backward Compatibility Module.
 
-def parse_markdown_to_ast(md_content: str):
-    # Enable table parsing and other common plugins
-    md = MarkdownIt("commonmark", {"tables": True}).enable(['table'])
-    tokens = md.parse(md_content)
-    # Convert to a JSON-serializable list of dicts (tokens are objects, so we dict-ify them recursively)
-    def token_to_dict(token):
-        d = {
-            'type': token.type,
-            'tag': token.tag,
-            'attrs': token.attrs,
-            'map': token.map,
-            'nesting': token.nesting,
-            'level': token.level,
-            'children': [token_to_dict(child) if child else None for child in token.children] if token.children else None,
-            'content': token.content,
-            'markup': token.markup,
-            'info': token.info,
-            'meta': token.meta,
-            'block': token.block,
-            'hidden': token.hidden
-        }
-        return {k: v for k, v in d.items() if v is not None}  # Remove None values for cleanliness
+This module re-exports from markitect.core.parser for backward compatibility.
+New code should import from markitect.core.parser directly.
+"""
 
-    return [token_to_dict(token) for token in tokens]
+# Re-export from core for backward compatibility
+from markitect.core.parser import parse_markdown_to_ast
+
+__all__ = ['parse_markdown_to_ast']