fix: restore the production gate after the migration tasks

- rebuild editors/vscode bundles, stale since the parser escape fix
- attach the caught ParseError as `cause` in both migration validators
- drop two unused test bindings flagged by eslint

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

editors/vscode/src/compiler.cjs

@@ -1,6 +1,6 @@
 "use strict";
 // Generated by scripts/build-editor-compiler.mjs. Do not edit directly.
-// WRN editor compiler source hash: 653a88ea2a34e9c446fc55b268f3ba9c5d27f9e114fc6aa9228ef560e1fd616d
+// WRN editor compiler source hash: 2987e8e9d91b793818a195395e740d35d0d5c2a320ff1c3a5ae77363850c7b8e
 // WRN editor compiler generator hash: a54ca847c758bc98d8e353ad6d70088df31de1820f6cf9d1c3462505f563e6b8
 // Generated with TypeScript: 6.0.3
 const __nodeRequire = require;
@@ -7069,12 +7069,13 @@ function parseHtmlView(src, pos) {
         if (quote !== '"' && quote !== "'")
             return fail("Expected a quoted attribute value");
         i++;
-        // Backslash-escapes the delimiter (and anything else) so an attribute
-        // value -- e.g. an `api="fn({ a: \"b\" })"` call expression -- can carry
-        // the same quote character it's wrapped in.
+        // Backslash escapes the delimiter -- so an attribute value such as the
+        // call expression `api="fn({ a: \"b\" })"` can carry the same quote
+        // character it's wrapped in -- and escapes itself. Every other backslash
+        // is a literal one, so a value like "C:\Users\name" survives intact.
         let value = "";
         while (i < src.length && src[i] !== quote) {
-            if (src[i] === "\\" && i + 1 < src.length) {
+            if (src[i] === "\\" && (src[i + 1] === quote || src[i + 1] === "\\")) {
                 value += src[i + 1];
                 i += 2;
                 continue;