Complete the 0.16.0 changelog

Author: luciusmagn

docs/releases/v0.16.0.md

@@ -67,4 +67,13 @@ keeping the two extension mechanisms independent.
 - MCP tools that require protocol task execution remain visible in status but
   are not exposed as callable Autolith tools.
 
+## Release reliability
+
+- Made binary archives byte-for-byte repeatable by constructing a minimal
+  synthetic Git identity without ambient templates, reflogs, stat-bearing
+  index entries, or asynchronous maintenance files.
+- Kept Nix's context-dependent SBCL selection inside the Nix launcher and
+  migrated stale Nix runtime records without disturbing source-managed
+  selections.
+
 [Full commit history](https://github.com/luciusmagn/autolith/compare/v0.15.1...v0.16.0)