feat(spaces): implement Phase 5 Directory Sync Mode

Implements directory synchronization for Information Spaces:

- SpaceDirectoryExporter: Export space to directory structure
  - Multiple variants: flat, hierarchical, by_path
  - Manifest generation for reimport
  - Incremental export (skip unchanged files)
  - Metadata file export
  - IncrementalExporter for change detection

- DirectorySpaceImporter: Import directory content into space
  - Recursive directory scanning
  - Multiple file pattern support
  - Conflict detection with strategies (skip/overwrite/rename)
  - Manifest-based import for intelligent reimport
  - Structure preservation in space paths

- BidirectionalSyncCoordinator: Two-way sync with conflict detection
  - Sync directions: space-to-directory, directory-to-space, bidirectional
  - Conflict resolution strategies: space_wins, directory_wins, newer_wins, manual, skip
  - Dry-run mode for preview
  - Orphan cleanup option
  - Event emission for progress tracking

45 unit tests covering all sync components.

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

markitect/spaces/sync/__init__.py

@@ -2,12 +2,63 @@
 Directory synchronization for Information Spaces.
 
 This package provides filesystem integration:
-- SpaceToDirectory exporter using VariantFactory
-- DirectoryToSpace importer
-- Bidirectional sync coordinator
-- Filesystem watcher for external changes
-- Conflict detection and resolution
+- SpaceDirectoryExporter: Export space to directory using variants
+- DirectorySpaceImporter: Import directory content into space
+- BidirectionalSyncCoordinator: Two-way sync with conflict detection
+- Conflict detection and resolution strategies
 """
 
-# Directory sync will be implemented in Phase 5
-__all__ = []
+from .exporter import (
+    SpaceDirectoryExporter,
+    IncrementalExporter,
+    ExportConfig,
+    ExportVariant,
+    ExportResult,
+    ExportedFile,
+)
+from .importer import (
+    DirectorySpaceImporter,
+    ManifestImporter,
+    ImportConfig,
+    ImportResult,
+    ImportedDocument,
+    ImportConflict,
+)
+from .bidirectional import (
+    BidirectionalSyncCoordinator,
+    SyncConfig,
+    SyncDirection,
+    ConflictResolution,
+    SyncResult,
+    SyncAction,
+    SyncConflict,
+    FileState,
+    create_sync_coordinator,
+)
+
+__all__ = [
+    # Exporter
+    "SpaceDirectoryExporter",
+    "IncrementalExporter",
+    "ExportConfig",
+    "ExportVariant",
+    "ExportResult",
+    "ExportedFile",
+    # Importer
+    "DirectorySpaceImporter",
+    "ManifestImporter",
+    "ImportConfig",
+    "ImportResult",
+    "ImportedDocument",
+    "ImportConflict",
+    # Bidirectional sync
+    "BidirectionalSyncCoordinator",
+    "SyncConfig",
+    "SyncDirection",
+    "ConflictResolution",
+    "SyncResult",
+    "SyncAction",
+    "SyncConflict",
+    "FileState",
+    "create_sync_coordinator",
+]