fix(contractor): space exhaustion in linear storage

[DennisOSRM]

fixes #7656

[Copilot]

🟡 Human review recommended

The change impacts core contraction-path witness search behavior and, while plausibly correct, warrants human verification on real-world datasets/regression scenarios due to potential knock-on effects (e.g., increased shortcuts).

Pull request overview

This PR addresses an intermittent osrm-contract failure (hang/segfault/assert) by adding a hard stop to the contractor’s witness search when the fixed-capacity LinearHashStorage backing the ContractorHeap approaches saturation, preventing the linear-probing hash from ever becoming completely full (which would otherwise risk an infinite probe loop).

Changes:

• Change the internal relaxNode helper to return a boolean “must stop” flag instead of void.
• Abort the witness search early when heap.Occupancy() reaches RELAXED_NODE_LIMIT, avoiding potential LinearHashStorage full-table linear-probing livelocks.

File summaries

File	Description
src/contractor/contractor_search.cpp	Adds an early-exit condition to prevent fixed-capacity heap storage saturation during contraction witness searches.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.15%. Comparing base (9fd8ab9) to head (4989923).

Files with missing lines	Patch %	Lines
src/contractor/contractor_search.cpp	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7673      +/-   ##
==========================================
+ Coverage   90.74%   94.15%   +3.41%     
==========================================
  Files         484      484              
  Lines       37688    37694       +6     
==========================================
+ Hits        34201    35492    +1291     
+ Misses       3487     2202    -1285     

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