Read files from captured Git commits

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Validation model implementation plan
 
-Status: In progress; the shared validation executor and internal diagnostics are complete.
+Status: In progress; the shared executor, internal diagnostics, and committed-file reader are complete.
 
 This plan implements the enabling work in [model.md](model.md), guided by
 [ADR 0003](../adr/0003-declarative-validation.md). It is written for a Luna
@@ -229,6 +229,10 @@ complete error text.
 
 ## Stage 3: Add committed candidate-file enumeration
 
+**Completion:** Complete. `internal/git` enumerates committed tree entries and
+blob sizes, while `internal/validation` exposes a lazy candidate-tree reader
+that serves blob bytes by object ID.
+
 **Outcome:** File-oriented validators can share an offline reader bound to the
 captured commit.