master red: tail.rs expects @floor as the first f64 refusal after #10405 #10413

Boundary

Master is red on t27b-native-linux and t27b-native-macos since 03c6be1 (PR #10410, see #10405). cli/t27b/tests/tail.rs f32_rounding_and_rem_call_their_ports changes the test source from f32 to f64 and expects @floor to be the first refusal. #10405 gave @floor and @ceil an f64 routine, so the first refusal is now @trunc:

t27b: unsupported construct ExprCall(@trunc) at line 4 (`@trunc`: libm.t27 has no f64 routine for it ...)

Only that test's expectation and its doc comment change. No lowering changes.

User Scenarios

• A contributor opens any PR against master and sees t27b-native-linux and t27b-native-macos fail on a test their change never touched.

Requirements

1. The f64 case expects ExprCall(@trunc) at line 4 with "no f64 routine".
2. The doc comment says that @round, @floor and @ceil have f64 routines.
3. Net 0 hand-written lines.

Success Criteria

• t27b-native-linux and t27b-native-macos pass on the fix PR, and tail.rs reports 25 passed.