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/language-server.cjs

@@ -1,5 +1,5 @@
 #!/usr/bin/env node
-// WRN editor language server source hash: 5702fe2c68d78698b5507beb585cfd66a1c826f5c9febddca09fc45c49e40d4e
+// WRN editor language server source hash: 8555261bb7933ee73d08cee279600fa64d2f35b35c5144ceba516e6929593d37
 // WRN editor language server generator hash: f593a44aaf05495b789ce7a3086bee1eebb951b884d41c0e017bbcfe5f547e72
 // @bun @bun-cjs
 (function(exports, require, module, __filename, __dirname) {var __create = Object.create;
@@ -195929,11 +195929,11 @@ function htmlDocument(document) {
 }
 function markdown(value) {
   if (typeof value === "string")
-    return value;
+    return value || undefined;
   if (value && typeof value === "object" && "value" in value) {
-    return String(value.value);
+    return String(value.value) || undefined;
   }
-  return "";
+  return;
 }
 function htmlCompletions(document, position) {
   if (!isInsideHtml(document, offsetAt2(document.text, position)))