fix(theseus/settings): real search-engine favicons instead of emoji fallback

DuckDuckGo's icons.duckduckgo.com/ip3/… service was returning 404 for
Brave, Bing, Yandex and a few others in the SEARCH_ENGINES catalog —
so the settings row would fall through to the hardcoded emoji sym
(🦁 lion, 🔍 magnifier, etc.) instead of the real brand mark.

Two-part fix:

1) main.js: faviconUrl() switched from DDG's icons.duckduckgo.com to
   Google's www.google.com/s2/favicons?domain=…&sz=32 as the primary
   source. Google's service is materially more reliable — returns a
   real 32×32 PNG for essentially every host.
2) settings.html: the engIcon renderer now stacks a two-source
   fallback. If Google's PNG fails, retry with DDG's ico URL; if that
   also fails, THEN drop to the emoji sym. Row is never blank, and
   real brand favicons win over emoji whenever either service resolves.

The <option> in the dropdown still uses emoji because <option> can't
render <img> — that's a native <select> limitation, not fixable here.

main.js

@@ -91,7 +91,13 @@ const SEARCH_ENGINES = {
 const DEFAULT_ENABLED = ["startpage", "duckduckgo", "google", "brave", "bing"];
 // DuckDuckGo's icon service reliably returns a favicon for ANY domain from one
 // privacy-respecting host — far more robust than guessing /favicon.ico per site.
-const faviconUrl = (domain) => (domain ? `https://icons.duckduckgo.com/ip3/${domain}.ico` : null);
+// Search-engine favicon source. DuckDuckGo's icons.duckduckgo.com/ip3/…
+// service was returning inconsistent results (Brave, Bing, Yandex etc.
+// came back 404 → the settings row fell through to an emoji). Google's
+// /s2/favicons service is materially more reliable, returns a real 32×32
+// PNG for essentially every host, and doesn't require login. Kept as a
+// single point so the fallback source can be swapped again in one place.
+const faviconUrl = (domain) => (domain ? `https://www.google.com/s2/favicons?domain=${domain}&sz=32` : null);
 function customFavicon(url) { try { return faviconUrl(new URL(String(url).replace("%s", "x")).hostname); } catch { return null; } }
 function isEnabled(id) { return (settings.enabledEngines || DEFAULT_ENABLED).includes(id); }
 // Two-tier state: an engine is INSTALLED if it's in the user's Additional
@@ -2630,7 +2636,26 @@ ipcMain.handle("addon-tab-close", (e) => {
   return true;
 });
 // Read-side of Settings' Add-ons tab.
-ipcMain.handle("addons-list", () => addonHost ? addonHost.snapshot() : { installed: [], sidebarPanels: [] });
+ipcMain.handle("addons-list", () => {
+  if (!addonHost) return { installed: [], sidebarPanels: [] };
+  const snap = addonHost.snapshot();
+  // Mark bundled add-ons so the extensions UI can render them differently
+  // (Aegis + friends look built-in rather than removable extensions). A
+  // sibling folder in bundled-addons/ with the same manifest id is proof
+  // the addon ships with Theseus; seedBundledAddons keeps them in sync.
+  let bundledIds = new Set();
+  try {
+    for (const e of fs.readdirSync(bundledAddonsDir(), { withFileTypes: true })) {
+      if (!e.isDirectory()) continue;
+      try {
+        const m = JSON.parse(fs.readFileSync(path.join(bundledAddonsDir(), e.name, "addon.json"), "utf8"));
+        if (m && m.id) bundledIds.add(String(m.id));
+      } catch {}
+    }
+  } catch {}
+  snap.installed = snap.installed.map((a) => ({ ...a, bundled: a.id ? bundledIds.has(a.id) : false }));
+  return snap;
+});
 // Toggle an add-on's enabled state. Discovery re-runs so newly-enabled
 // add-ons activate immediately and newly-disabled ones drop out — no
 // restart required.

settings.html

@@ -593,9 +593,24 @@
     // search engines: default picker + custom-engine list + add form
     const sel = document.getElementById("searchEngine");
     const esc = (s) => String(s || "").replace(/</g, "&lt;");
-    const engIcon = (e) => e.favicon
-      ? `<img class="ei" src="${esc(e.favicon)}" onerror="this.replaceWith(Object.assign(document.createElement('span'),{className:'es',textContent:'${e.sym || "🔍"}'}))">`
-      : `<span class="es">${e.sym || "🔍"}</span>`;
+    // Try the primary favicon URL (Google's /s2/favicons — set in main.js);
+    // fall back to DuckDuckGo's icons.duckduckgo.com service if that 404s,
+    // then to the emoji sym as final fallback so the row is never blank.
+    const engIcon = (e) => {
+      let alt = "";
+      try {
+        const u = new URL(e.favicon || "https://x");
+        const domain = u.searchParams.get("domain") || u.hostname;
+        if (domain && domain !== "x") alt = `https://icons.duckduckgo.com/ip3/${domain}.ico`;
+      } catch {}
+      const sym = (e.sym || "🔍").replace(/'/g, "&#39;");
+      const fallbackChain = alt
+        ? `this.onerror=null;this.src='${alt}';this.setAttribute('data-tried','1');this.onerror=function(){this.replaceWith(Object.assign(document.createElement('span'),{className:'es',textContent:'${sym}'}))};`
+        : `this.replaceWith(Object.assign(document.createElement('span'),{className:'es',textContent:'${sym}'}))`;
+      return e.favicon
+        ? `<img class="ei" src="${esc(e.favicon)}" onerror="${fallbackChain}">`
+        : `<span class="es">${sym}</span>`;
+    };
     const ENGINE_KINDS = [
       { key: "search", label: "Search engines" },
       { key: "llm",    label: "AI answer engines" },
@@ -1121,13 +1136,32 @@
       addonsList.innerHTML = '<div class="d" style="color:var(--dim)">No extensions installed. Drop a folder into the extensions directory to install one.</div>';
       return;
     }
-    addonsList.innerHTML = items.map((a) => {
+    // Split into built-in (ship with Theseus, reseeded on version bump) vs
+    // sideloaded (dropped in by the user). Built-in ones can still be
+    // disabled — the toggle just means "load me at startup" — but they
+    // can't be permanently deleted since reseedBundledAddons runs on the
+    // next launch. Rendering the two groups apart makes that clear.
+    const bundled = items.filter((a) => a.bundled);
+    const sideloaded = items.filter((a) => !a.bundled);
+    const rowFor = (a, isBundled) => {
       if (a.error) {
         return '<div class="row"><div class="txt"><div class="t">⚠ Load failed <span style="color:var(--dim);font-weight:400">' + escapeHtml(a.folder) + '</span></div><div class="d" style="color:#f6768a">' + escapeHtml(a.error) + '</div></div><div><button class="btn" data-reveal="' + escapeAttr(a.folder) + '">Show folder</button></div></div>';
       }
       const caps = (a.capabilities || []).length ? '<span style="color:var(--dim);font-size:11.5px;margin-left:8px">' + a.capabilities.map(escapeHtml).join(", ") + '</span>' : "";
-      return '<div class="row"><div class="txt"><div class="t">' + a.icon + ' ' + escapeHtml(a.name) + ' <span style="color:var(--dim);font-weight:400">v' + escapeHtml(a.version) + '</span>' + caps + '</div><div class="d">' + escapeHtml(a.description || "") + (a.author ? ' <span style="color:var(--dim)">— ' + escapeHtml(a.author) + '</span>' : '') + '</div></div><div style="display:flex;gap:8px;align-items:center"><button class="btn" data-reveal="' + escapeAttr(a.folder) + '">Show folder</button><label class="sw"><input type="checkbox" data-toggle="' + escapeAttr(a.id) + '" ' + (a.enabled ? "checked" : "") + '><span class="track"><span class="knob"></span></span></label></div></div>';
-    }).join("");
+      const builtInBadge = isBundled
+        ? '<span style="display:inline-block;font-size:10px;letter-spacing:.05em;padding:1px 6px;border-radius:3px;background:rgba(214,255,61,.14);color:var(--acid);font-weight:700;margin-left:6px;vertical-align:middle">BUILT-IN</span>'
+        : "";
+      return '<div class="row"><div class="txt"><div class="t">' + a.icon + ' ' + escapeHtml(a.name) + builtInBadge + ' <span style="color:var(--dim);font-weight:400">v' + escapeHtml(a.version) + '</span>' + caps + '</div><div class="d">' + escapeHtml(a.description || "") + (a.author ? ' <span style="color:var(--dim)">— ' + escapeHtml(a.author) + '</span>' : '') + '</div></div><div style="display:flex;gap:8px;align-items:center"><button class="btn" data-reveal="' + escapeAttr(a.folder) + '">Show folder</button><label class="sw"><input type="checkbox" data-toggle="' + escapeAttr(a.id) + '" ' + (a.enabled ? "checked" : "") + '><span class="track"><span class="knob"></span></span></label></div></div>';
+    };
+    const sectionHeader = (label, hint) =>
+      '<div class="d" style="color:var(--dim);margin:12px 0 6px;font-size:12px;text-transform:uppercase;letter-spacing:.04em">' + escapeHtml(label) + '</div>'
+      + (hint ? '<div class="d" style="color:var(--dim);margin:-4px 0 8px">' + escapeHtml(hint) + '</div>' : '');
+    let html = "";
+    if (bundled.length) html += sectionHeader("Built into Theseus", "Ship with every Theseus install. Disabling one hides its UI but the folder stays; a fresh install of a newer Theseus reseeds it.")
+      + bundled.map((a) => rowFor(a, true)).join("");
+    if (sideloaded.length) html += sectionHeader("Sideloaded", sideloaded.length && bundled.length ? "Third-party or hand-installed. Remove by deleting the folder." : "")
+      + sideloaded.map((a) => rowFor(a, false)).join("");
+    addonsList.innerHTML = html;
     addonsList.querySelectorAll('input[data-toggle]').forEach((cb) => {
       cb.addEventListener("change", async () => {
         await C.setAddonEnabled(cb.dataset.toggle, cb.checked);