feat(spaces): implement Phase 8 Git History Tracking

Implements optional git-based version control for information spaces:
- HistoryConfig model for configuring history tracking
- Commit, Branch, HistoryEntry, DiffResult models
- IHistoryBackend and IHistoryQuery interfaces
- GitHistoryBackend using git CLI for version control
- GitHistoryEventHandler for event-driven auto-commits
- HistoryEventCoordinator for managing space history
- HistoryQueryService for high-level history queries
- Automatic commits on DOCUMENT_ADDED/REMOVED/CONTENT_CHANGED events
- Support for:
  * Commit log with pagination and filtering
  * Diff between versions
  * File content at specific versions
  * Branch creation and switching
  * Version restoration
  * Uncommitted changes detection
- 43 comprehensive unit tests with git availability checks

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

markitect/spaces/history/__init__.py

@@ -1,13 +1,43 @@
 """
-Git history tracking for Information Spaces (Optional Phase 8).
+History tracking module for Information Spaces.
 
-This package provides version control integration:
-- IHistoryBackend: Abstract history backend interface
-- GitHistoryBackend: Git implementation
-- Event-driven commit triggers
-- History query API (log, diff, branches)
-- Versioned read/render operations
+Provides optional git-based version control for space content,
+enabling commit history, diffs, and version restoration.
 """
 
-# History tracking will be implemented in Phase 8
-__all__ = []
+from .models import (
+    Commit,
+    Branch,
+    HistoryEntry,
+    DiffResult,
+    DiffLine,
+    DiffType,
+    HistoryConfig,
+)
+from .interfaces import (
+    IHistoryBackend,
+    IHistoryQuery,
+)
+from .git_backend import GitHistoryBackend, GitError
+from .events import GitHistoryEventHandler, HistoryEventCoordinator
+from .queries import HistoryQueryService
+
+__all__ = [
+    # Models
+    "Commit",
+    "Branch",
+    "HistoryEntry",
+    "DiffResult",
+    "DiffLine",
+    "DiffType",
+    "HistoryConfig",
+    # Interfaces
+    "IHistoryBackend",
+    "IHistoryQuery",
+    # Implementations
+    "GitHistoryBackend",
+    "GitError",
+    "GitHistoryEventHandler",
+    "HistoryEventCoordinator",
+    "HistoryQueryService",
+]