docs: reconcile project state and refresh README

memory/project_ui_architecture.md

@@ -246,3 +246,28 @@ ordinary `ObjectUpdated` events complete inventory work.
 
 `GameWindow` now constructs and forwards narrow lifecycle edges to these
 owners; no selection algorithm or interaction request body belongs there.
+
+## 2026-07-27 M4 world-interaction checkpoint
+
+The six-slice world-interaction plan lives at
+`docs/plans/2026-07-23-world-interaction-completion.md`. Slices 1–3 are
+user-accepted:
+
+- the favorite-spell bar owns its authored overflow controls and stable manual
+  offset;
+- status Use/Assess shares canonical interaction and appraisal owners;
+- `gmFloatyExaminationUI` is an independent top-level window, not a shared
+  primary-panel page;
+- object assessment owns exact response flags, balanced busy lifetime,
+  selection-follow, inscription, complete EoR item/creature/spell reports, and
+  the animated private creature preview;
+- retained items and favorite spells select on button-down; right-click uses
+  the correct object-appraisal or local spell-report path;
+- component-disabled ACE profiles show the accepted scarab/prismatic formula,
+  DAT icon DIDs, authored foreground stack, and 310 x 400 window extent.
+
+Resume at Slice 4. It must add equipped-child world picking through the
+existing completed render-selection frame and exact child presentation key;
+do not invent a second selection state or marker anchor. Slices 5–6 then add
+vendor browsing and server-authoritative transactions through the same Runtime
+inventory/action owners.