Fix dual-module bug in playground dev rewrite

The playground's dev-mode rewrite sent 'squint-cljs/core.js' through
/js/squint-local/core.js (the 38-byte root shim that re-exports from
./src/squint/core.js). Vite transformed that shim's relative import
into a /@fs/.../src/squint/core.js URL.

Meanwhile the same import inside already-served runtime files
(test.js, multi.js, etc.) was left as a bare specifier and resolved by
the browser via the importmap to /src/squint/core.js. Two URLs, same
file — and ES-module caching treats them as two separate modules.
Each gets its own _metaSym; with-meta written through the user side
becomes invisible to meta reads inside the runtime, which is why
deftest'd tests surfaced as 'anonymous' in :begin-test-var events.

Rewrite 'squint-cljs/{,src/squint/}X' straight to /src/squint/X so
user code and importmap-resolved imports converge on one URL, one
module instance. Confirmed against a live Vite+Playwright repro:
before, sameModule=false; after, sameModule=true and deftest names
surface correctly end-to-end.

Author: borkdude

playground/public/js/main_js.mjs

@@ -108,8 +108,18 @@ let evalCode = async (code) => {
       // opaque origin that can't resolve relative specifiers. Anchor on the
       // page origin — import.meta.url can point to an unexpected bundle path
       // under Vite.
-      const localBase = `${window.location.origin}/js/squint-local/`;
-      js = js.replaceAll("'squint-cljs/", `'${localBase}`);
+      //
+      // Route everything through /src/squint/ (matching the importmap) so
+      // user-compiled code and the runtime modules (test.js, multi.js) end
+      // up importing the SAME URL for core.js. Previously user code went
+      // via /js/squint-local/core.js → Vite-transformed shim →
+      // /@fs/.../src/squint/core.js, while the runtime's bare specifier
+      // resolved via the importmap to /src/squint/core.js — two URLs,
+      // two ES-module instances, two _metaSym symbols, and with-meta
+      // written through one was invisible to meta in the other.
+      const base = `${window.location.origin}/src/squint/`;
+      js = js.replaceAll("'squint-cljs/src/squint/", `'${base}`);
+      js = js.replaceAll("'squint-cljs/", `'${base}`);
     }
     JSEditor(js);
     if (!repl) {