fix: filter out global namespace from citation chips

[senamakel-droid]

This PR fixes issue tinyhumansai#1121 where assistant messages showed an unintended "global 100%" citation chip.

Changes

• Updated app/src/pages/conversations/components/CitationChips.tsx to explicitly filter out citations with the global namespace before they are mapped and rendered.
• Re-evaluates whether to return null if the remaining filtered list of citations is empty, preventing a blank citation container.

Testing

• Confirmed that npm run test successfully passes the full test suite in app/.

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PR created automatically by Jules for task 11407212333738798334 started by @senamakel-droid

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Note

Low Risk
Low risk UI-only change that filters a specific citation namespace before rendering; main risk is unintentionally hiding legitimate citations if upstream labeling changes.

Overview
Filters assistant message citations to exclude those with the global namespace before rendering chips in CitationChips.

Updates the empty-state logic to return null when all citations are filtered out, preventing an empty citation container from showing.

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