Add packed integer vector support

[Malkovsky]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 97.19101% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.23%. Comparing base (6f1be75) to head (deb5a8d).

Files with missing lines	Patch %	Lines
include/pixie/integer_vector/packed.h	92.81%	4 Missing and 7 partials ⚠️
include/pixie/integer_vector/monotone.h	96.49%	0 Missing and 2 partials ⚠️
src/tests/integer_vector_tests.cpp	99.29%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
+ Coverage   90.76%   91.23%   +0.46%     
==========================================
  Files          49       53       +4     
  Lines       12414    12920     +506     
  Branches     1783     1826      +43     
==========================================
+ Hits        11268    11787     +519     
+ Misses        534      521      -13     
  Partials      612      612              

Flag	Coverage Δ
gcov	91.23% <97.19%> (+0.46%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-06T12:45:46.245659Z	deb5a8d	New commits

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.