fix: tree agent rendering of fluid handles (#26292)

[jenn-le]

This fixes a bug where tree agent does not render fluid handles.

Cherry picked from: #26292

[github-actions]

Warning

WARNING: This PR is targeting a release branch!

All changes must first be merged into main and then backported to the target release branch.
Please include a link to the main PR in the description of this PR.

Changes to release branches require approval from the Patch Triage group before merging.
You should have already discussed this change with them so they know to expect it.

For more details, see our internal documentation for the patch policy and processes for
patch releases.

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  252163 links
    1804 destination URLs
    2045 URLs ignored
       0 warnings
       0 errors

[noencke]

This change is extremely low risk, and will unblock tree-agent dev work in Copilot Boards.