feat(analysis): live SSE updates in the admin coverage dashboard

The Analysis section now reflects worker progress in real time:

- Opens an EventSource on the live stream while mounted; a "Live" pill
  reflects connection state and reconnects on drop (probes after repeated
  failures so a lost session logs out).
- Applies events incrementally: enqueued marks in-scope loaded pages
  queued; started flips a chip to a pulsing "analyzing"; completed flips
  it green and live-bumps the manga + chapter coverage badges (guarded so
  no double count); failed flips it red. A compact activity ticker shows
  the last few events.
- Server numbers stay authoritative: re-loading the overview or a page
  grid clears the matching live overrides.

API client: analysisStatusStreamUrl() + AnalysisEvent type.

Tests: vitest for the stream URL; Playwright asserts SSE frames flow into
the ticker (existing coverage/drill/queue specs get a default quiet
stream). svelte-check + build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/api/admin.test.ts

@@ -32,7 +32,8 @@ import {
     getAnalysisMangaCoverage,
     getAnalysisChapterCoverage,
     getAnalysisChapterPages,
-    getAnalysisPageDetail
+    getAnalysisPageDetail,
+    analysisStatusStreamUrl
 } from './admin';
 
 function ok(body: unknown, status = 200): Response {
@@ -580,4 +581,10 @@ describe('admin crawler api client', () => {
         expect(url).toMatch(/\/v1\/admin\/analysis\/pages\/p1$/);
         expect(d.status).toBe('none');
     });
+
+    it('analysisStatusStreamUrl points at the SSE endpoint', () => {
+        expect(analysisStatusStreamUrl()).toMatch(
+            /\/v1\/admin\/analysis\/status\/stream$/
+        );
+    });
 });

frontend/src/lib/api/admin.ts

@@ -532,3 +532,27 @@ export async function getAnalysisPageDetail(
         `/v1/admin/analysis/pages/${encodeURIComponent(pageId)}`
     );
 }
+
+/** One live analysis event from the SSE stream. */
+export type AnalysisEvent =
+    | {
+          kind: 'enqueued';
+          count: number;
+          manga_id: string | null;
+          chapter_id: string | null;
+      }
+    | {
+          kind: 'started' | 'completed' | 'failed';
+          page_id: string;
+          manga_id: string;
+          chapter_id: string;
+          page_number: number;
+      };
+
+/** URL of the live analysis SSE stream. Open with `new EventSource(...)`
+ *  while the admin Analysis page is mounted and close it on navigate-away.
+ *  Each message is a named `analysis` event whose `data` is an
+ *  {@link AnalysisEvent}; a `lagged` event signals dropped frames. */
+export function analysisStatusStreamUrl(): string {
+    return apiUrl('/v1/admin/analysis/status/stream');
+}