Implement trait-based handling for infix operators

[neysofu]

Summary

• rename the std equality trait to Equality and introduce new operator traits plus trait-based impls for Char, AsciiChar, and String
• update compiler resolver/ir normalization so infix syntax dispatches through trait calls rather than hardwired builtin paths while keeping primitive scalars reserved
• refresh docs, instructions, and snapshots/fixtures to reflect the new trait surface

Testing

• Not run (not requested)