feat(editor-v2): editor.js glue (mount, submit-capture, files alias)

Un-bundled progressive-enhancement glue:
- DOMContentLoaded → mount cm6 on every textarea[data-editor-language].
- Each <form> gets one capture-phase submit handler that copies every
  contained editor's getValue() into its textarea.value before the
  browser serializes the form (submit-time copy bridge).
- The textarea with class files-editor-content (the files-modal
  textarea) exposes its controller as window.__filesEditor for
  files-overlay.js's getValue / setContent / setLanguage calls.
- 'auto' language resolves from the modal's filename input
  ([data-editor-filename]); a language [data-editor-language-select]
  dropdown lets the user override.
- Vocab fetched lazily on the first srccfg mount; cached for the page.

Falls through silently if window.__editor isn't defined (bundle
failed to load), keeping the raw textarea visible — no-JS fallback.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

l4d2web/l4d2web/static/js/editor.js

@@ -0,0 +1,84 @@
+// Un-bundled. Driven by data-editor-language attrs on <textarea>.
+// Mounts cm6 (from editor.bundle.js exporting window.__editor),
+// installs one capture-phase submit handler per <form>, and exposes
+// a named alias for the files-editor modal.
+(function () {
+  "use strict";
+  if (!window.__editor || typeof window.__editor.mount !== "function") {
+    return;  // bundle didn't load — graceful no-JS fallback
+  }
+
+  let vocabPromise = null;
+  function loadSrccfgVocab() {
+    if (!vocabPromise) {
+      vocabPromise = fetch("/static/data/srccfg-vocab.json", { credentials: "same-origin" })
+        .then(r => r.ok ? r.json() : Promise.reject(new Error("vocab fetch failed: " + r.status)))
+        .catch(err => { console.warn("[editor] vocab load failed", err); return null; });
+    }
+    return vocabPromise;
+  }
+
+  function resolveAutoLanguage(filenameInput) {
+    const name = (filenameInput && filenameInput.value || "").toLowerCase();
+    if (name.endsWith(".cfg")) return "srccfg";
+    if (name.endsWith(".sh"))  return "bash";
+    return "plain";
+  }
+
+  async function mountOne(textarea) {
+    let lang = textarea.getAttribute("data-editor-language") || "plain";
+    let filenameInput = null;
+    let dropdown = null;
+    if (lang === "auto") {
+      const modal = textarea.closest("#files-editor-modal") || document;
+      filenameInput = modal.querySelector("[data-editor-filename]");
+      dropdown = modal.querySelector("[data-editor-language-select]");
+      lang = resolveAutoLanguage(filenameInput);
+    }
+
+    const vocab = (lang === "srccfg") ? await loadSrccfgVocab() : null;
+    const controller = window.__editor.mount(textarea, { language: lang, vocab });
+
+    // Submit-time copy bridge
+    const form = textarea.closest("form");
+    if (form && !form.__editorSubmitBound) {
+      form.__editorSubmitBound = true;
+      form.addEventListener("submit", () => {
+        for (const ta of form.querySelectorAll("textarea[data-editor-language]")) {
+          if (ta.__editorController) ta.value = ta.__editorController.getValue();
+        }
+      }, true /* capture phase */);
+    }
+    textarea.__editorController = controller;
+
+    // Files-modal hooks
+    if (textarea.classList.contains("files-editor-content")) {
+      window.__filesEditor = controller;
+      if (dropdown) {
+        dropdown.addEventListener("change", () => {
+          const v = dropdown.value;
+          controller.setLanguage(v === "auto" ? resolveAutoLanguage(filenameInput) : v);
+        });
+      }
+      if (filenameInput) {
+        filenameInput.addEventListener("input", () => {
+          if (!dropdown || dropdown.value === "auto") {
+            controller.setLanguage(resolveAutoLanguage(filenameInput));
+          }
+        });
+      }
+    }
+  }
+
+  function init() {
+    for (const ta of document.querySelectorAll("textarea[data-editor-language]")) {
+      mountOne(ta).catch(err => console.error("[editor] mount failed", err));
+    }
+  }
+
+  if (document.readyState === "loading") {
+    document.addEventListener("DOMContentLoaded", init);
+  } else {
+    init();
+  }
+})();