The `swift` LanguageDescriptor closure built several `contains:`
arrays with long `[Mode] + [Mode] + …` concatenation chains (root
node, `tuple`, `functionParameters`, `typeDeclaration`, string
interpolation submodes). Overloaded `+` chains cost the type checker
exponentially, and these expressions sat right at the timeout limit:
`swift test` on macOS passed, but the slower/older `xcodebuild`
toolchains failed the iOS/watchOS and DocC jobs with
"the compiler is unable to type-check this expression in reasonable
time".

Hoist each chain into an explicitly-typed `[Mode]` local so `+`
resolves directly to `Array.+` instead of exploring overloads. Pure
refactor: token output is unchanged (all 21 Swift fidelity fixtures
pass), and the two failing CI commands (`xcodebuild docbuild` and the
iOS Simulator build) now succeed locally. The heaviest expression
drops from a 17ms monolithic `+` chain to an 11ms plain constructor
call.