feat(embed,ui04): E07 acceptance — matrix completion, hostile-CSS hardening, measurements and record closure

- E07 e2e (7 cases): 4-viewport fixed size, narrow shrink + dual-slot 12px stack, single/static + empty state + two-photo loop copies, broken-thumb drop, reducedMotion stop with manual arrows, forged postMessage rejected, hostile CSS (!important box-sizing/border) with inline-important countermeasures + duplicate script dedup
- loader v2: geometry-critical properties upgraded to inline !important (beats host stylesheet !important)
- pre-existing fixes: likes.spec view-count assertion vs concurrent session's AlbumHeader unicode icons (toContainText); embed-v2 host port moved to 3998 (3999 collides with embed-crossorigin under parallel full runs); prettier formatting of two concurrent-session files (formatting-only)
- evidence: matrix EMB-A01..A16 closed in acceptance record (mechanism-level items honestly marked), measurements (loader v2 9885B/gzip 3959B, first-load 1 GET + 1 WS, DOM<=16), refreshed screenshots/recordings, master plan UI-04 note
- regression: root lint/typecheck/test 12 packages green; embed suites 43/43; admin embed-slots 5/5; journey pre-existing env failure reproduced at clean HEAD (registered)

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

apps/admin/e2e/embed-slots.spec.ts

@@ -228,9 +228,7 @@ test.describe.serial('embed slot management (P4b Task 5)', () => {
     // 真实 EmbedStream（.stream-viewport）且模拟点赞出心形（WYSIWYG 证据）。
     await expect(page.getByTestId('embed-preview-v2-iframe')).toBeVisible()
     await expect(page.getByTestId('embed-preview-sim-like')).toBeVisible()
-    const previewFrame = page
-      .frames()
-      .find((f) => f.url().includes('/embed-preview'))
+    const previewFrame = page.frames().find((f) => f.url().includes('/embed-preview'))
     expect(previewFrame).toBeDefined()
     await expect(previewFrame!.locator('.stream-viewport')).toHaveCount(1)
     await page.getByTestId('embed-preview-sim-like').click()