Fix #404: Support parameter substitution in structural types and PolyFunction for Scala 3

[Emanuelgm1998]

Problem
TagMacro on Scala 3 failed to correctly substitute type parameters in two cases:
Structural refinement types — when a type like { type T = Int } was part of a combined tag, the resolved type members were computed but never passed to refinedTag, causing incorrect tags to be generated.
PolyFunction types — the macro was attempting to transform native Scala 3 polymorphic function types (scala.PolyFunction), which Scala 3 already handles correctly, causing the tag shape to be altered incorrectly.
Solution
Added a guard for scala.PolyFunction in the AppliedType match case, so native polymorphic function types are passed directly to createTag without transformation.
Fixed the Refinement case to pass resolvedTypeMemberLtts as a map to refinedTag instead of Map.empty, ensuring resolved type members are included in the generated tag.
Tests
All 209 tests passing locally on Scala 3 (JVM).
Scala 2 (2.11, 2.12, 2.13) builds unaffected.
should basic support for polymorphic function types ✅
should can resolve parameters in structural types ✅
should other type members' bounds are not malformed when resolving parameters in structural types ✅

/claim #404

[Emanuelgm1998]

Hi @neko-kai and @pshirshov,

I’ve attached a short video showing all tests passing as requested. This should confirm that the issues with parameter substitution in structural types and PolyFunction for Scala 3 are now resolved.

Whenever you have a moment, it’d be great to get your final review. Thanks a lot!

Screen_Recording_20260407_235600_Chrome.mov