POC package metadata search

[kevinemoore]

First implementation of package metadata search. This only supports exact matches on metadata fields and only searches latest versions of packages.

Description

TODO

• Unit tests
• Security: Confirm that this change meets security best practices and does not violate the security model
• Open and Embed: Confirm that this change doesn't break Open variant and Embed widget
• Documentation
  • run optipng on any new PNGs
  • Python: Run build.py for new docstrings
  • JavaScript: basic explanation and screenshot of new features
  • Markdown somewhere in docs/**/*.md that explains the feature to end users (said .md files should be linked from SUMMARY.md so they appear on https://docs.quilt.bio)
  • Markdown docs for developers
• Changelog entry (skip if change is not significant to end users, e.g. docs only)

[codecov]

Codecov Report

❌ Patch coverage is 3.61446% with 80 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.20%. Comparing base (d171f02) to head (a723d49).

Files with missing lines	Patch %	Lines
api/python/quilt3/packages.py	3.61%	80 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4619      +/-   ##
==========================================
- Coverage   40.28%   40.20%   -0.09%     
==========================================
  Files         886      886              
  Lines       37857    37940      +83     
  Branches     6182     6180       -2     
==========================================
+ Hits        15251    15254       +3     
- Misses      21356    22177     +821     
+ Partials     1250      509     -741     

Flag	Coverage Δ
api-python	90.65% <3.61%> (-1.02%)	⬇️
catalog	21.29% <ø> (ø)
lambda	92.66% <ø> (ø)
py-shared	97.18% <ø> (ø)

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[QuiltSimon]

Reconciliation pass (see #engineering thread, 2026-08-29): this is the oldest open draft in the repo (300+ days, last touched 2025-10-27) and it reads as a completed POC rather than a mergeable change — three of its four files are planning docs under api/python/quilt3/specs/ (a directory that doesn't exist on master), and the TODO checklist (tests, security review, docs) is unchecked.

Recommending: extract the design thinking in package_search_metadata.md into an issue and close. But it's your call, @kevinemoore — since you're active in the repo again (#5249), a one-line answer settles it: does package metadata search have a future as a quilt3 API, or has the catalog-side metadata sort/search work (#5164 → #5189 lineage) covered the need? If the former, an issue preserves the design without a rotting draft; if the latter, this closes clean.