Add segmented sliding-window storage

[Malkovsky]

• Updated storage API to return array of two spans rather then single span
• Introduced sliding window storage

[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 2026-09-02T21:18:36.872207Z	c18cf17	New commits

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 27d7b3cd1f

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[chatgpt-codex-connector]

Document the new storage extension-point requirements

Add canonical Doxygen contracts for begin_position_impl(), end_position_impl(), and both segments_impl() variants. The facade now requires these hooks—and serialization depends on them—but only documents the public wrappers, leaving implementers without the required invariants for absolute positions, range validation, segment ordering, and lifetime/invalidation behavior. Concrete-class comments do not replace the CRTP extension-point contract.

AGENTS.md reference: AGENTS.md:L86-L92

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[codecov]

Codecov Report

❌ Patch coverage is 97.50000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.96%. Comparing base (2a43cde) to head (c18cf17).

Files with missing lines	Patch %	Lines
include/pixie/storage.h	93.33%	0 Missing and 2 partials ⚠️
include/pixie/storage/sliding_window.h	95.74%	1 Missing and 1 partial ⚠️
include/pixie/split_span.h	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #65      +/-   ##
==========================================
+ Coverage   90.66%   90.96%   +0.30%     
==========================================
  Files          47       49       +2     
  Lines       12220    12395     +175     
  Branches     1771     1778       +7     
==========================================
+ Hits        11079    11275     +196     
+ Misses        533      518      -15     
+ Partials      608      602       -6     

Flag	Coverage Δ
gcov	90.96% <97.50%> (+0.30%)	⬆️

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