docs: update STATE with 2026-04-03 session work

XSS fix: panelName sanitized with DOMPurify in detached.html.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.machine_readable/STATE.scm

@@ -67,4 +67,8 @@
         "Completed Tauri→Gossamer migration (270 commands)"
         "Fixed ReScript build errors (open keyword, indexOf, duplicate symbols)"
         "Added 13 placeholder panel views for GSA/Burble/IDApTIK"
-        "Moved back button to top-right pill"))))
+        "Moved back button to top-right pill"))
+    (session "2026-04-03"
+      (focus "XSS security fix")
+      (changes
+        "panelName sanitized with DOMPurify in detached.html to prevent XSS"))))