feat(infospace): add structured evaluation output with history and diffing (S1.5)

Add data models (ScoreEntry, EntityEvaluation, EvaluationSnapshot,
SnapshotDiff) and I/O utilities for YAML frontmatter evaluation files,
snapshot persistence, history append, and snapshot diffing.

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

markitect/infospace/__init__.py

@@ -21,6 +21,24 @@ from .validator import (
     validate_entities,
     validate_entity,
 )
+from .evaluation import (
+    EntityEvaluation,
+    EvaluationSnapshot,
+    MetricChange,
+    MetricValue,
+    ScoreChange,
+    ScoreEntry,
+    SnapshotDiff,
+)
+from .evaluation_io import (
+    append_to_history,
+    diff_snapshots,
+    read_entity_evaluation,
+    read_history,
+    read_snapshot,
+    write_entity_evaluation,
+    write_snapshot,
+)
 
 __all__ = [
     "EntityMeta",
@@ -38,4 +56,20 @@ __all__ = [
     "ComplianceResult",
     "validate_entities",
     "validate_entity",
+    # Evaluation models
+    "EntityEvaluation",
+    "EvaluationSnapshot",
+    "MetricChange",
+    "MetricValue",
+    "ScoreChange",
+    "ScoreEntry",
+    "SnapshotDiff",
+    # Evaluation I/O
+    "append_to_history",
+    "diff_snapshots",
+    "read_entity_evaluation",
+    "read_history",
+    "read_snapshot",
+    "write_entity_evaluation",
+    "write_snapshot",
 ]