fix(search): correct export citation loading and selection handling

[thostetler]

Search-page citation export had two issues: exporting all showed an empty/placeholder state for several seconds before results appeared, and after exporting a subselection it was impossible to export all records because the previous subset's qid was reused.

• Surface a loading state during the initial export fetch in useCitationExporter and consume it in CitationExporter
• Render a loading skeleton on the export page until the search data and the client are ready, removing the static-to-interactive hydration swap
• Gate the vault qid navigation on selected mode so export all uses the plain query and ignores a stale cached qid; preserve the selection
• Add tests for the initial loading state and the selection/qid handling

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.4%. Comparing base (6a15785) to head (3be10e0).

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #881     +/-   ##
========================================
+ Coverage    61.2%   61.4%   +0.3%     
========================================
  Files         348     348             
  Lines       41373   41405     +32     
  Branches     1826    1839     +13     
========================================
+ Hits        25297   25412    +115     
+ Misses      16033   15948     -85     
- Partials       43      45      +2     

Files with missing lines	Coverage Δ
...c/components/CitationExporter/CitationExporter.tsx	76.8% <100.0%> (+0.3%)	⬆️
...components/CitationExporter/useCitationExporter.ts	98.2% <100.0%> (+5.0%)	⬆️
src/components/ResultList/ListActions.tsx	85.2% <100.0%> (+7.2%)	⬆️

... and 7 files with indirect coverage changes

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.