[fix]: Fix synced skills suggested add button tint

[zzj3720]

Summary

• fix suggested synced-skill Add buttons to use the live system accent when the app accent is set to Default
• keep explicit user-selected accent colors unchanged
• add an e2e-mode home-directory override and UI regression covering the suggested-folder Add button

Fixes #19.

Validation

• make -C sandbox-vm framework
• cd web && yarn install --immutable && yarn build:embedded
• cd macos && ENABLE_PREVIEWS=YES bash DevKit/Scripts/workspace_test_unit.sh
• cd macos && ENABLE_PREVIEWS=YES xcodebuild test -workspace OpenBridge.xcworkspace -scheme OpenBridge -configuration UnsignedDebug -destination 'platform=macOS' -skipPackagePluginValidation -skipMacroValidation -resultBundlePath .build/TestResults/SyncedSkillsSettingsUITests.xcresult -only-testing:OpenBridgeUITests/SyncedSkillsSettingsUITests/testSuggestedAddButtonUsesVisibleAccentTint ENABLE_TESTABILITY=YES PRODUCT_BUNDLE_IDENTIFIER=app.openbridge.unsigneddebug PROVISIONING_PROFILE_SPECIFIER='' CODE_SIGN_STYLE=Manual CODE_SIGNING_ALLOWED=YES CODE_SIGNING_REQUIRED=NO CODE_SIGN_IDENTITY=- DEVELOPMENT_TEAM=''
• minimachine UI validation on codex/issue19-black-bar: Settings → Synced Skills shows suggested Add buttons in blue/system accent instead of black; clicking Add moves the folder into Sync Folders

Notes

• Local make -C sandbox-vm vm was not run successfully because the local Docker daemon/socket was unavailable; the framework build and macOS app/UI validation passed.