fix(models): stop the catalog sync from erasing its own output

collectEntries() computed each model's "current" capabilities with the
previous catalog still installed, so every delta was measured against the
last one. An upstream value that still agreed with what we had written
looked like no change and was dropped: the second run cut `providers`
from 20 entries to 5, taking glm-5.3's 1M context correction with it.

The baseline has to be the hand-written tables alone, so the reader is
detached for the snapshot and restored in a finally — a mid-sync failure
must not leave capabilities.js without it.

Two smaller corrections:

- One vote per provider in the modality tally. Ids that normalize to the
  same model (claude-opus-4-thinking:1024, :8192, :32768 …) were each
  counted, giving nano-gpt five votes where other gateways had one. No
  model's result actually flipped — the variants agree with each other —
  but the majority rule only means something if the denominator does.
- Restore the etag from the file on startup. It lived only in module
  state, so every restart re-downloaded 4.3MB to be told nothing changed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/modelCatalog/sync.js

@@ -85,9 +85,14 @@ function build(catalog, entries) {
   const tally = {};
   for (const [providerId, provider] of Object.entries(catalog)) {
     const models = {};
+    const counted = new Set();
     for (const [modelId, model] of Object.entries(provider?.models || {})) {
       const id = baseId(modelId);
       models[id] = model;
+      // One vote per provider: several ids can normalize to the same model
+      // (claude-opus-4-thinking:1024, :8192, :32768 …) and must not stack.
+      if (counted.has(id)) continue;
+      counted.add(id);
       const counts = tally[id] || (tally[id] = { total: 0 });
       counts.total++;
       for (const input of model?.modalities?.input || []) {
@@ -134,14 +139,18 @@ function build(catalog, entries) {
   return { models, providers };
 }
 
-// Snapshot every registered model with its currently resolved capabilities, so
-// build() can tell which upstream values are actually a change.
+// Snapshot every registered model with the capabilities the hand-written tables
+// resolve on their own, so build() can tell which upstream values are a change.
+//
+// The previous catalog MUST be detached first. Leaving it installed makes each
+// delta relative to the last one, so a value that still agrees with upstream
+// looks like "no change" and is dropped — the file erases itself over two runs.
 async function collectEntries() {
-  const [{ default: registry }, { getCapabilitiesForModel }] = await Promise.all([
+  const [{ default: registry }, { getCapabilitiesForModel, setCatalogSource }] = await Promise.all([
     import("open-sse/providers/registry/index.js"),
     import("open-sse/providers/capabilities.js"),
   ]);
-  await installCatalogSource();
+  setCatalogSource(null);
 
   const entries = [];
   for (const provider of registry) {
@@ -176,7 +185,8 @@ export async function syncModelCatalog() {
       // point — not worth a worker thread.
       const catalog = await response.json();
       const etag = response.headers.get("etag") || null;
-      const { models, providers } = build(catalog, await collectEntries());
+      const entries = await collectEntries();
+      const { models, providers } = build(catalog, entries);
       const serialized = JSON.stringify({ v: 1, etag, syncedAt: Date.now(), models, providers });
 
       writeAtomic(CATALOG_FILE, serialized);
@@ -203,14 +213,28 @@ export async function syncModelCatalog() {
     console.log(`[modelCatalog] sync failed: ${state.lastError}`);
     return null;
   } finally {
+    // collectEntries() detaches the reader; put it back whatever happened.
+    await installCatalogSource().catch(() => {});
     state.running = false;
   }
 }
 
+// The etag lives in the file we wrote, so a restart can resume from it instead
+// of re-downloading 4.3MB to be told nothing changed.
+function restoreEtag() {
+  try {
+    state.etag = JSON.parse(fs.readFileSync(CATALOG_FILE, "utf8")).etag || null;
+    state.lastSync = fs.statSync(CATALOG_FILE).mtimeMs;
+  } catch {
+    state.etag = null;
+  }
+}
+
 // Schedule the recurring sync. Disable entirely with MODEL_CATALOG_SYNC=off.
 export function startModelCatalogSync() {
   if (timer) return;
   if (String(process.env.MODEL_CATALOG_SYNC || "").toLowerCase() === "off") return;
+  restoreEtag();
 
   const schedule = (delay) => {
     timer = setTimeout(async () => {