v0.11

Fix VM move forwarding bug with if-expression result registers

Move forwarding was incorrectly forwarding through phi-like merge
points where a register has multiple definitions from different
branches of an if-expression. This caused DCE to eliminate the
then-branch body, producing wrong results.

Example: `if v0 > 0 { 0 - 100 } else { v0 }` returned the else
branch value regardless of the condition.

Fix: skip forwarding when the source register (move_src) has multiple
definitions, since the Move acts as a merge point that must be
preserved so all control flow paths reach the destination.

Found by differential fuzzing (JIT vs VM).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>