Add efficiency report and optimize coordinate reversal in WalkAlong

[danfma]

Add efficiency report and optimize coordinate reversal in WalkAlong

Summary

This PR adds a comprehensive efficiency analysis report documenting 10+ performance optimization opportunities across the DotTerritory codebase, and implements one specific optimization to demonstrate the approach.

Key changes:

• New file: EFFICIENCY_REPORT.md - comprehensive analysis of allocation and LINQ-related performance bottlenecks
• Code fix: Optimized Territory.WalkAlong() method to replace Reverse().ToArray() with more efficient Array.Reverse() approach

The optimization eliminates an unnecessary intermediate IEnumerable<Coordinate> allocation when walking along a line with negative distance, reducing GC pressure in a hot path operation.

Review & Testing Checklist for Human

⚠️ IMPORTANT: This change was not tested locally due to missing .NET SDK in dev environment

• Run tests and verify behavior - Especially WalkAlongTest.WalkAlong_NegativeDistance which directly exercises the modified code path
• Verify behavioral equivalence - Confirm that Array.Reverse(coords.ToArray()) produces identical results to coords.Reverse().ToArray() for edge cases (empty arrays, single coordinates, etc.)
• Review efficiency report accuracy - Spot-check a few of the identified issues in the report to validate the analysis is sound

Recommended Test Plan

1. Run full test suite: dotnet test src/DotTerritory.sln
2. Specifically verify these WalkAlong test scenarios pass:
   • WalkAlong_NegativeDistance (exercises the fixed code)
   • WalkAlong_Loop and WalkAlong_OneAndHalfLoop (verify no regressions)
3. Consider running a quick benchmark on WalkAlong with negative distances to validate the performance claim

Notes

• The efficiency report documents 9 additional optimization opportunities for future PRs
• This optimization targets a hot path operation (coordinate walking) that's likely called frequently in geospatial calculations
• Session: https://app.devin.ai/sessions/078e83b75da94204a924a2d1a8ac826c
• Requested by: @danfma (Daniel Ferreira Monteiro Alves)

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[Copilot]

Pull Request Overview

This PR adds a comprehensive performance analysis document and implements an optimization to reduce memory allocations in the Territory.WalkAlong() method.

• Adds EFFICIENCY_REPORT.md documenting 10 performance optimization opportunities across the codebase
• Optimizes coordinate reversal in WalkAlong() to eliminate intermediate IEnumerable<Coordinate> allocation
• Replaces Reverse().ToArray() pattern with more efficient Array.Reverse() approach

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/DotTerritory/Territory.Along.cs	Optimizes coordinate reversal by using in-place Array.Reverse() instead of LINQ operations
EFFICIENCY_REPORT.md	Comprehensive analysis documenting allocation bottlenecks and performance optimization opportunities

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[Copilot]

Date appears to be incorrect - report shows October 6, 2025 but current date should be in 2024 or early 2025.

Suggested change

	**Report Generated:** October 6, 2025
	**Report Generated:** June 6, 2024