fix: Duplicate skills now follow stable source priority

[hatayama]

Summary

• Duplicate skill names now resolve using a stable source priority.
• Unity skill discovery now guarantees the same ordered-root structure as the native CLI.

User Impact

• When the same skill name exists in multiple roots, the earlier configured source consistently wins.
• Assets remain ahead of direct packages, direct packages ahead of manifest-local packages, and manifest-local packages ahead of PackageCache entries.

Changes

• Store normalized source roots in an ordered list while using a separate ordinal set only for deduplication.
• Added a behavior test covering each adjacent priority boundary available in a temporary project.
• Kept CLI-only root behavior unchanged; its current-project-only gate is not exposed through a test-only seam.

Verification

• Characterization approach: the priority test passed before the implementation on the current Mono runtime, because its present HashSet behavior happens to preserve insertion order. The change removes reliance on that unspecified API behavior rather than reproducing a deterministic failure.
• dist/darwin-arm64/uloop compile --project-path <PROJECT_ROOT> (0 errors, 0 warnings)
• SkillInstallLayoutTests (11 passed)
• ToolSkillSynchronizerTests (52 passed)
• git diff --check

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 9e3499e7-24f7-4a83-828a-1db1d59da9e6

📥 Commits

Reviewing files that changed from the base of the PR and between 49f0302 and 0629486.

📒 Files selected for processing (2)

• Assets/Tests/Editor/SkillInstallLayoutTests.cs
• Packages/src/Editor/Infrastructure/SkillSetup/SkillSourceRootEnumerator.cs

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📝 Walkthrough

Walkthrough

SkillSourceRootEnumerator now returns skill source roots in deterministic discovery order via an ordered list combined with a deduplication set, replacing prior HashSet iteration. A new test validates that GetSkillSourceInfos resolves overlapping skill names from the earlier-precedence source root, using a new WriteSourceSkill test helper.

Changes

Deterministic Source Root Ordering

Layer / File(s)	Summary
Ordered root enumeration Packages/src/Editor/Infrastructure/SkillSetup/SkillSourceRootEnumerator.cs	EnumerateSkillSourceRoots and AddSkillSourceRoot are reworked to build an orderedRoots list alongside a seenRoots set, normalizing paths and yielding roots in discovery order.
Precedence test coverage Assets/Tests/Editor/SkillInstallLayoutTests.cs	Adds GetSkillSourceInfos_WhenNamesOverlap_PrefersEarlierSourceRoot and a WriteSourceSkill helper to verify overlapping skill names resolve ToolName from the earlier-precedence source root.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• hatayama/unity-cli-loop#951: Directly affects the layout-aware skill source discovery logic introduced in SkillInstallLayout that this PR tests and reorders.
• hatayama/unity-cli-loop#980: Both PRs touch SkillInstallLayout skill-source resolution and precedence behavior.
• hatayama/unity-cli-loop#1588: Both PRs extend SkillInstallLayoutTests.cs to validate GetSkillSourceInfos behavior for overlapping skill names across source roots.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: making duplicate skill resolution follow stable source priority.
Description check	✅ Passed	The description is directly related to the changeset and accurately describes the source-priority fix and verification.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ 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/hatayama/preserve-skill-source-root-order

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[cubic-dev-ai]

No issues found across 2 files

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