refactor(testing): 清理低风险重复支撑代码

[iamsyc]

Summary

• 删除 resolution 旧兼容 shim，ResolutionSelection 改用 preset.logicalSize
• 收敛重复测试支撑代码到共享 support target
• 新增 VoidDisplaySharingTestingSupport 和 VoidDisplayVirtualDisplayTestingSupport
• 更新相关测试 target 依赖与显式 imports

Validation

• scripts/ci/full_regression.sh --out-dir .ai-tmp/reduce-low-risk-cleanup/pr-full-regression
• Swift tests: 547 passed
• Go packages: 2 passed
• Xcode Debug build: passed
• Xcode UI tests: 15 total, 0 failed, 2 skipped by real-environment gate
• arm64 Release smoke: passed

Notes

• No app-facing text changed; localization resources did not need updates.
• The branch ref was published through GitHub Git Data API after HTTPS git push hit transient GitHub transport failures.

[github-actions]

CI Summary

Run: Open

Check	Status	Details
Change Scope	ui_code	code=true, ui=true
Dependency Review	success	code PR gate; high and critical vulnerabilities block
Static Checks	success	actionlint, shellcheck, shfmt, SwiftFormat, SwiftLint, action pinning
Head Script Self-Test	skipped	runs for script/tooling PRs; script=false
Unit Tests	success	Swift tests: 547 Go packages: 2 Reason: passed Artifact: unit-gate
Xcode Build	success	Debug build with zero warning scan Artifact: xcode-build
UI Smoke	success	Failure classification is written by ui-smoke-summary.json in each artifact. Artifacts: ui-smoke-baseline, ui-smoke-permissionDenied, ui-smoke-rebuildFailed
Release Smoke	success	Artifacts: release-smoke-arm64, release-smoke-intel64 Release verify summaries are produced by release.yml before publishing.
Artifacts	link	Open artifacts
CI Gate	success	single branch protection check