Fix R5900 SQRT.S source register

[GTTeancum]

Summary

• emit R5900 SQRT.S from the encoded t source register
• add a code-generation regression test with distinct s and t fields

Why

The current translator reads s, but the R5900 SQRT.S fd, ft encoding uses t; s is otherwise unused. This produced valid but incorrect camera normalization in X-Men Legends and left its animated title-level view matrix effectively broken.

Testing

• focused CodeGenerator test passes
• regenerated X-Men Legends camera code now takes both square roots from the computed operands
• runtime verification reaches the title level with an animated, nonidentity view matrix and renders the Cerebro chamber