Preserve empty deletion spans in debug ledger

docs/roadmap/implementation.md

@@ -2,7 +2,7 @@
 
 **Last updated:** 2026-09-25
 
-**Status:** In progress; Stages 1–2 complete.
+**Status:** In progress; Stages 1–3 complete.
 **Source baseline:** `a83a518` (feature roadmap); application baseline `0b6cd98`.
 **Audience:** gpt-5.6-terra coding agent.
 
@@ -271,6 +271,12 @@ existing configured-secret redaction and debug-off persistence coverage.
 **End state:** Debug evidence distinguishes a proposed/applied deletion from an
 absent proposal or an edit that was never applied.
 
+**Completed 2026-09-25.** Candidate-backed ledger entries now preserve an
+explicit empty proposed replacement, and applied entries preserve an explicit
+empty applied replacement. Serialized disposition coverage and the specified
+focused package tests passed; the artifact contract documents the fields and
+validator identity change.
+
 ## Stage 4 — Verify the Integrated Contract and Finish Documentation
 
 **Work**