collab-presence 0010: unified draggable overlay menu

One circular FAB (peer-count badge) replaces the top-right overlay row:
draggable anywhere (pointer capture, 4px click-vs-drag threshold — the
comment-pin pattern), position persisted in localStorage, panel opens
toward screen center and stacks composable sections — roster, source chip,
view-only pill, follow row, comments, chrome toggle. Renders at z-50 above
everything (decided: covers wx dialogs; trivially dismissed via click-away/
Esc/drag). CommentLayer portals its bar + list panel into the menu's
comments slot; pins/popovers/composer/click-catcher stay canvas-anchored.
The FAB is the chrome-hidden survivor. e2e specs updated with an
openOverlayMenu helper (panel is closed by default, click-away closes it).

NOTE: Playwright suites updated but not executed here (no local WASM
artifacts) — verify on CI / next session.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A42xfPFNdfsUt9eowkC9eM

tests/web/comments-viewport-resize.spec.ts

@@ -1,4 +1,5 @@
 import { test, expect, type Page } from '@playwright/test';
+import { openOverlayMenu } from './overlay-menu';
 
 /**
  * Comment pins vs. canvas resize (collab-presence 0005 regression): the DOM
@@ -28,6 +29,7 @@ async function bootAs(page: Page, user: string): Promise<void> {
       intervals: [1000],
     })
     .toMatch(TITLE);
+  await openOverlayMenu(page); // the comment bar lives in the overlay menu (0010)
   await expect(page.getByTestId('comment-bar-toggle')).toBeVisible({ timeout: 30000 });
   await page.getByTestId('comment-bar-toggle').click();
   await expect(page.getByTestId('comment-mode-toggle')).toBeVisible();