Stream model pull progress via SSE instead of fire-and-forget

Replace the asyncio.create_task() fire-and-forget pattern for model
downloads with SSE streaming that relays Ollama's pull progress in
real time. The frontend now shows live download percentage instead of
a static "Pulling..." label with blind polling.

- routes/chat.py: SSE streaming endpoint with 1800s timeout
- stores/settings.ts: pullModel uses apiStreamPost with onProgress callback
- SettingsView.vue: live "Downloading 42%" display, removed polling/setTimeout
- summary.md: updated to reflect SSE streaming for model pulls

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/stores/settings.ts

@@ -1,6 +1,6 @@
 import { ref, computed } from "vue";
 import { defineStore } from "pinia";
-import { apiGet, apiPut, apiPost } from "@/api/client";
+import { apiGet, apiPut, apiPost, apiStreamPost } from "@/api/client";
 import type { AppSettings } from "@/types/settings";
 
 export const useSettingsStore = defineStore("settings", () => {
@@ -45,8 +45,13 @@ export const useSettingsStore = defineStore("settings", () => {
     }
   }
 
-  async function pullModel(model: string) {
-    await apiPost("/api/chat/models/pull", { model });
+  async function pullModel(
+    model: string,
+    onProgress?: (data: Record<string, unknown>) => void,
+  ) {
+    await apiStreamPost("/api/chat/models/pull", { model }, (data) => {
+      if (onProgress) onProgress(data);
+    });
   }
 
   async function deleteModel(model: string) {