chore: support grouped collections on project home

[stevenle]

Motivation

• Ensure the project home page supports grouped collection hierarchies the same way the collection list page does, so collections can be organized by group on the main Root CMS landing page.

Description

• Replaced the manual card-based collection list in ProjectPage.CollectionList with the existing CollectionTree component to render groups and nested collections (packages/root-cms/ui/pages/ProjectPage/ProjectPage.tsx).
• Pass window.__ROOT_CTX.collections and the current projectId into CollectionTree and removed the unused IconFolder import.
• Simplified styles by removing the previous card-specific rules and adding a lightweight wrapper .ProjectPage__collectionTree { max-width: 580px; } (packages/root-cms/ui/pages/ProjectPage/ProjectPage.css).
• Modified files: packages/root-cms/ui/pages/ProjectPage/ProjectPage.tsx, packages/root-cms/ui/pages/ProjectPage/ProjectPage.css.

Testing

• Attempted to run the dev server with pnpm -C packages/root-cms dev, but the run failed due to a corepack/network error fetching pnpm (proxy HTTP tunneling 403), so runtime verification could not be completed.

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Codex Task

[stevenle]

surgical change to get the project page to group the collections properly.

before:

after:

primarily a style-only change so no review needed (will be updating this page to be more ai task oriented in the future)