087 phantom literal suffix

// Test (ASPIRATIONAL, MUST_RUN, currently failing): parser accepts phantom
// literal-suffix syntax `<label>` on a literal in arg-value position.
//
// Parser must:
//   1. Recognize `32<celsius>` as `literal=32, phantom=celsius` at the
//      arg-value position
//   2. Strip the `<celsius>` for Zig emission (per "no phantoms in Zig-code")
//   3. Forward `celsius` as the value's phantom for the phantom checker
//
// The `<>` syntax was chosen precisely because `>` at end of expression
// without a RHS doesn't fit Zig grammar — koru's parser can claim the
// suffix unambiguously.
//
// MINIMAL parser-focused pin: just accept the syntax, no conversion math.
//
// See `docs/UNITS_OF_MEASURE.md` "Implementation sketch" — literal-suffix
// parsing is item (6) in the implementation plan.

~import std/io

~event accept-celsius { c: f32<celsius> }
| ok f32<celsius>

~accept-celsius => ok c

~accept-celsius(c: 32<celsius>)
| ok v |> std/io:print.ln("{{ v:f }}")