VS Code extension installs via a hand-built .vsix (from dev 83e472a96e36)

Folder copies into ~/.vscode/extensions no longer load in modern VS Code;
make_vsix.sh packages the extension (bash + python3 only) and the README
installs it with `code --install-extension`.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tst/editor_test.sh

@@ -211,6 +211,28 @@ else
     echo "(no Node runtime — the VS Code extension test is skipped; the language server is still tested)"
 fi
 
+# --- the VS Code .vsix package builds with the full payload ----------------
+# (the no-marketplace install path; needs only bash + python3)
+mkdir -p "$OUT/vsix"
+cp -R "$EDIT_DIR/vscode" "$EDIT_DIR/shared" "$OUT/vsix/"
+if ( cd "$OUT/vsix/vscode" && ./make_vsix.sh >/dev/null 2>&1 ) && \
+   PYTHONDONTWRITEBYTECODE=1 python3 -c "
+import sys, zipfile
+names = set(zipfile.ZipFile('$OUT/vsix/vscode/klammertext.vsix').namelist())
+need = {'extension.vsixmanifest', '[Content_Types].xml',
+        'extension/package.json', 'extension/extension.js',
+        'extension/language-configuration.json', 'extension/README.md',
+        'extension/klammertext_edit.py', 'extension/klammertext_ls.py',
+        'extension/syntaxes/klammertext.tmLanguage.json'}
+sys.exit(1 if need - names else 0)
+"; then
+    echo "${green}PASS${reset} vscode .vsix package builds (make_vsix.sh)"
+    PASS=$((PASS + 1))
+else
+    echo "${red}FAIL${reset} vscode .vsix package builds (make_vsix.sh)"
+    FAIL=$((FAIL + 1))
+fi
+
 # --- compare ---------------------------------------------------------------
 for f in $INDENT_FIXTURES $ALIGN_FIXTURES; do
     check "$f (python)"            "$OUT/$f.py.out"  "$FIX/${f}_expected.kt"