Spec explorer data endpoint, spec file finder, browser render test (failing)

- Add spec-explorer-data-by-slug helper with _SPEC_SLUG_MAP
- _find_spec_file searches spec/, web/, shared/sx/ref/ directories
- defpage specs-explore-page uses :data for server-side data fetch
- test_evaluator_renders_in_browser: failing test for client-side rendering
  (client re-evaluates defpage content, find-spec unavailable — pre-existing)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/test_page_render.js

@@ -0,0 +1,18 @@
+const path = require("path");
+const fs = require("fs");
+require(path.join(__dirname, "../_build/default/browser/sx_browser.bc.js"));
+require(path.join(__dirname, "sx-platform.js"));
+const K = globalThis.SxKernel;
+for (const n of ["signals","deps","page-helpers","router","adapter-html"])
+  K.loadSource(fs.readFileSync(path.join(__dirname,`../../../web/${n}.sx`),"utf8"));
+K.loadSource(fs.readFileSync("/tmp/comp_defs.txt","utf8"));
+
+const pageSx = fs.readFileSync("/tmp/page_sx.txt","utf8");
+const parsed = K.parse(pageSx);
+const html = K.renderToHtml(parsed[0]);
+if (typeof html === "string" && !html.startsWith("Error:")) {
+  console.log("SUCCESS! Rendered", html.length, "chars of HTML");
+  console.log("Preview:", html.substring(0, 200));
+} else {
+  console.log("Error:", html);
+}

hosts/ocaml/browser/test_signals.js

@@ -0,0 +1,25 @@
+const path = require("path");
+const fs = require("fs");
+require(path.join(__dirname, "../_build/default/browser/sx_browser.bc.js"));
+require(path.join(__dirname, "sx-platform.js"));
+const K = globalThis.SxKernel;
+for (const n of ["signals","deps","page-helpers","router","adapter-html"])
+  K.loadSource(fs.readFileSync(path.join(__dirname,`../../../web/${n}.sx`),"utf8"));
+
+// Test signal basics
+const tests = [
+  '(signal 42)',
+  '(let ((s (signal 42))) (deref s))',
+  '(let ((s (signal 42))) (reset! s 100) (deref s))',
+  '(let ((s (signal 10))) (swap! s (fn (v) (* v 2))) (deref s))',
+  '(let ((s (signal 0))) (computed (fn () (+ (deref s) 1))))',
+  '(let ((idx (signal 0))) (let ((c (computed (fn () (+ (deref idx) 10))))) (deref c)))',
+];
+
+for (const t of tests) {
+  const r = K.eval(t);
+  const s = JSON.stringify(r);
+  console.log(`${t.substring(0,60)}`);
+  console.log(`  => ${s && s.length > 100 ? s.substring(0,100) + '...' : s}`);
+  console.log();
+}