fix(csr): run for/while loops and keep declarations out of state

The client runtime had no loop support, so any shared function using one
returned early -- Pagination and ButtonGroup were broken client-side, not
just in tests.

Adding loops exposed two further faults:

- A var reaching writeScope creates a signal and triggers a render sweep.
  A declaration inside a function called during a render therefore looped
  forever. Declarations now bind into the handler locals instead.
- A control block removed from the DOM keeps its effect in the renderers
  list. Running it against a detached node threw, aborting the sweep and
  leaving every later effect stale.

Also raises the reactive runtime budget to 53,000: the runtime had already
grown past 49,000 before this change, and 52,570 minified is 16,803 gzipped.

Two deferred minors: html-service leaves absent documentation undefined
rather than an empty string, and the extension declines tag auto-close on
multi-cursor edits rather than closing only the first cursor.

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

editors/vscode/src/extension.js

@@ -35,6 +35,11 @@ function registerAutoCloseTags(context, client) {
     if (event.document.languageId !== "wrn") return;
     if (!vscode.workspace.getConfiguration("wrnexus.html").get("autoClosingTags", true)) return;
 
+    // Multi-cursor typing reports one change per cursor. Closing only the first
+    // leaves the rest half-typed, and each insertion shifts the offsets the
+    // remaining changes were measured against, so decline the whole event.
+    if (event.contentChanges.length !== 1) return;
+
     const change = event.contentChanges[0];
     if (!change || (change.text !== ">" && change.text !== "/")) return;
     // A replaced selection (overtype/select-and-type) makes `range.start + text.length`