release: 3.39.0 — decoded-editing batch

Bump VERSION/pyproject/PWA header to 3.39.0 and the SW cache to
simple-v484 (index.html + help changed).  CHANGELOG [3.39.0] folds the
unreleased 3.38.2 start-script fix and documents the decoded-editing
batch: DF-context resolution, EF.ECC/EF.AD split, path-based selection,
EF.SST tri-state editor, the Services editor + path-exact FS check, and
the UST 147-150 completion.

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simple-v483';
+const CACHE = 'simple-v484';
 const URLS = [
   'index.html',
   'help.html',