[jonluca]

Summary

Preserve valid pixel aspect ratios whose rational components exceed 256. A 712×574 frame declaring 759:712 should display as 759×574, but the component cap discarded that declaration and displayed square pixels.

What changed

• Bound the ratio's magnitude using overflow-safe integer arithmetic, preserving precise and unreduced representations.
• Keep the existing frame-aware display-aspect gate and invalid/non-positive guards.
• Extend the existing SAR suites with precise ratios, scaled boundary values and Int32 extremes; update the architecture description and changelog.

Test plan

• Device / OS: Apple M4 Max, macOS 27.0.1, Xcode 27.1.
• Source media: deterministic synthetic SAR/frame geometry, including 759:712 on 712×574; no external media required.
• Red run: the added regression cases fail against the unchanged upstream policy (12 failed expectations).
• Green run: 47 tests across the focused SAR, container-resolution and hardware-decoder aspect suites pass.
• python3 Scripts/check-doc-links.py and git diff --check pass.

Checklist

• CHANGELOG.md updated
• Conventional commit
• Fix lives in the engine
• No public API change

[Copilot]

🟢 Approval recommended

The narrow arithmetic change safely handles Int32 components, retains existing safeguards, and has focused regression coverage with no identified blocking issues.

No open issues 🎉

What changed in this PR

This PR fixes the engine’s pixel-aspect validation so precise ratios such as 759:712 are preserved instead of falling back to square pixels.

Changes:

• Replace component limits with overflow-safe ratio-magnitude bounds while retaining existing validation safeguards.
• Add regression cases for precise ratios, scaled boundaries, and Int32 extremes.
• Update test terminology, architecture documentation, and the changelog.

File	Description
Tests/​AetherEngineTests/​Issue290DisplayAspectGateTests.swift	Update comments and test terminology to describe the magnitude gate.
Tests/​AetherEngineTests/​Issue177SARLatchTests.swift	Add precision, boundary, and display-aspect regression cases.
Sources/​AetherEngine/​Decoder/​PixelAspectPolicy.swift	Bound ratio magnitude using Int64 arithmetic while preserving declared components.
docs/​architecture.md	Document the revised pixel-aspect gate.
CHANGELOG.md	Record the precise pixel-aspect correction.

_{Review effort: Balanced}