perf: hand out the cached dataset on an empty search

[funkadelic]

clearing a search reuses the sorted order already worked out instead of rechecking every row

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Summary by cubic

Clearing a search now reuses the cached dataset instead of recopying every row, so the sort cache can skip its subset walk on an empty term.

• getCities and getFilms now return the frozen cached array for the empty search term instead of a copy.
• loadEnvelope freezes the cached array, since callers now share it and a mutation would reorder every later caller's rows.
• Public result types are now readonly to reflect that callers don't own a mutable array.

^{Written for commit 236e7b4. Summary will update on new commits.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a847aa9) to head (236e7b4).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #116   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           48        48           
  Lines          773       773           
  Branches       145       145           
=========================================
  Hits           773       773           

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[codspeed]

Merging this PR will not alter performance

✅ 27 untouched benchmarks

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_{Comparing perf/share-the-cached-dataset-on-an-empty-search (236e7b4) with main (a847aa9)}

[codecov]

Bundle Report

Changes will increase total bundle size by 11 bytes (0.0%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
yart	5.04MB	11 bytes (0.0%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: yart

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
assets/src-*.js	21 bytes	262.11kB	0.01%
assets/movies-*.js	-5 bytes	1.94kB	-0.26%
assets/index-*.js	-5 bytes	1.64kB	-0.3%

[github-actions]

Lighthouse, median of 3 mobile runs

Page	Score	FCP	LCP	TBT	CLS	Speed Index
Cities	100	1.1s	1.4s	20ms	0.000	1.1s
Films	94	1.1s	3.0s	4ms	0.000	1.1s

Full reports

[cubic-dev-ai]

All reported issues were addressed across 8 files

<sub>Reply with feedback, questions, or to request a fix.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud