docs(plan): record what Phase 4 landed and the one error it leaves

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UDCbcCZQepnpSQYJ6SxxZm

lefthook.yml

@@ -31,10 +31,10 @@ pre-commit:
         fi
 
     # frontend/bindings is generated by `wails3`, not `go generate`, so
-    # the check above does not cover it.  ~20s: v3's generator is a
-    # static analyser over the whole package graph, where v2's built the
-    # app with a `bindings` tag and ran it.  Slower than v2's ~1.5s and
-    # still the cheapest place to catch a renamed field.
+    # the check above does not cover it.  ~3.5s warm, ~20s on a cold
+    # build cache: v3's generator is a static analyser over the whole
+    # package graph, where v2's built the app with a `bindings` tag and
+    # ran it.
     bindings-check:
       glob: "*.go"
       run: ./scripts/bindings-check.sh