RTC: Enforce peer limit per post instead of globally (#47919)

The `withRoomLimit` wrapper was monitoring awareness changes on all
rooms, including collection rooms (objectId === null) that are shared
across posts. This caused the peer limit to act as a global cap: e.g.
3 users on post A + 2 on post B would breach the limit of 3 in the
shared collection room and disconnect the newest editors.

Skip awareness monitoring on collection rooms so the limit is only
enforced on entity rooms, which are scoped per post.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/23947491000

Upstream-Ref: Automattic/jetpack@8779639

Author: mmtr

docs/manifests/components.html

@@ -582,7 +582,7 @@ <h1>Manifest Debugger</h1>
 <main>
   <div class="wrap">
     <div class="note ok" style="margin-bottom: 16px;">
-              Using <code>react-docgen-typescript</code>. Generation took <strong>6.4s</strong>.
+              Using <code>react-docgen-typescript</code>. Generation took <strong>6.8s</strong>.
             </div>
     <h2 class="section-title">Components</h2>
     <div class="grid" role="list">

docs/manifests/components.json

@@ -1 +1 @@
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+{"generatedAt":1775222382812,"hasCustomBabel":false,"hasCustomWebpack":false,"hasStaticDirs":true,"hasStorybookEslint":false,"refCount":1,"knownPackages":{"testPackages":{"@storybook/addon-vitest":"10.3.3","@testing-library/dom":"10.4.1","@vitest/browser-playwright":"4.1.1","playwright":"1.58.2","vitest":"4.1.1"}},"hasRouterPackage":false,"packageManager":{"type":"pnpm","version":"10.28.2","agent":"pnpm","nodeLinker":"undefined"},"typescriptOptions":{"reactDocgen":"react-docgen-typescript"},"preview":{"usesGlobals":false},"framework":{"name":"@storybook/react-vite","options":{}},"builder":"@storybook/builder-vite","renderer":"@storybook/react","portableStoriesFileCount":0,"applicationFileCount":0,"storybookVersion":"10.3.3","storybookVersionSpecifier":"10.3.3","language":"typescript","storybookPackages":{"@storybook/react-vite":{},"storybook":{}},"addons":{"@storybook/addon-docs":{},"@storybook/addon-a11y":{},"@storybook/addon-vitest":{}},"packageJsonType":"module"}