fix(mister): launch 3DO CHD with correct MGL slot

[wizzomafizzo]

Summary

• add .chd to the MiSTer 3DO generated-MGL slot
• change the 3DO disk slot index to 0 to match the core S0 mount slot
• add regression coverage for 3DO CHD MGL params and generated MGL output

Validated with go test ./pkg/platforms/mister/cores ./pkg/platforms/mister/mgls.

Fixes #805

Summary by CodeRabbit

• New Features

  • 3DO system now supports .chd disk image format alongside existing .iso and .cue formats

• Tests

  • Added regression test coverage for 3DO .chd disk images
  • Improved test path construction for better cross-platform reliability

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ac3c844f-ab14-4d20-b3ba-8981afe16c47

📥 Commits

Reviewing files that changed from the base of the PR and between 0310c1a and 61ee879.

📒 Files selected for processing (3)

• pkg/platforms/mister/cores/cores.go
• pkg/platforms/mister/cores/cores_test.go
• pkg/platforms/mister/mgls/mgls_test.go

---

📝 Walkthrough

Walkthrough

This PR fixes 3DO CHD disk image support by updating the system configuration to recognize .chd files, setting the correct slot index value, and adding regression test coverage with cross-platform-compatible test path construction.

Changes

3DO CHD Support

Layer / File(s)	Summary
3DO CHD slot configuration and validation pkg/platforms/mister/cores/cores.go, pkg/platforms/mister/cores/cores_test.go	3DO system slot extends supported extensions to include .chd and updates MGLParams.Index from 1 to 0; new table-driven test case validates the parsed MGL parameters for .chd files.
Cross-platform test path construction pkg/platforms/mister/mgls/mgls_test.go	Saturn and 3DO CHD test cases now build input paths using filepath.Join with OS-specific separators instead of hardcoded Unix-style paths, ensuring tests work on all platforms.

Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly Related PRs

• ZaparooProject/zaparoo-core#786: Adds .chd extension support to 3DO launcher with overlapping changes to slot index and path-to-MGL parsing logic.

Poem

🐇 A little .chd for 3DO so bright,
Index zero now does the trick just right,
Cross-platform paths with Separator's care,
Test coverage blooms with love to spare!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(mister): launch 3DO CHD with correct MGL slot' accurately describes the main change: fixing 3DO CHD launching with the correct MGL slot configuration.
Linked Issues check	✅ Passed	The PR implements all required objectives from issue #805: adds .chd support for 3DO, changes disk slot index to 0, and includes regression tests for MGL parameters.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing 3DO CHD support in the MiSTer platform: core slot configuration, test coverage, and generated MGL output.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/issue-805-mister-3do-chd

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[sentry]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!