docs: README + TODO split; trim CLAUDE.md; fix async form 415

hive-c0re/assets/async_forms.js

@@ -14,9 +14,12 @@
         btn.innerHTML = '<span class="spinner">◐</span>';
       }
       try {
+        // axum's `Form` extractor wants application/x-www-form-urlencoded;
+        // FormData would send multipart/form-data and bounce with 415.
         const resp = await fetch(form.action, {
           method: form.method || 'POST',
-          body: new FormData(form),
+          headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+          body: new URLSearchParams(new FormData(form)),
           redirect: 'manual',
         });
         const ok = resp.ok