jit: fix recursive call return value type tagging - #8499

Assisted-by: Codex:5.6-sol

• Closes #xxxx
• This PR follows our AI policy

Summary

Recursive call results were previously hardcoded as JitValue::Int(...). Even when Cranelift gave back a value with the right machine type, the JIT still wrote it down as an integer at compile time.

As a result, recursive functions returning bool or float were incorrectly typed. Functions with no return value could also try to read a return slot that was not there.

• Use slice pattern matching on return slots so we don't index into a nonexistent result
• Match the declared return type (self.sig.ret) with the actual return slot to preserve bool, float, and None return types
• Return NotSupported when the declared return type and actual return slot do not match
• Add regression tests for recursive functions returning bool and float
  • recursive_float: verifies that a recursive call result remains tagged as Float, allowing the following / 2.0 operation to consume the underlying F64 value correctly
  • recursive_bool: verifies that a recursive call result remains tagged as Bool (I8), allowing the following not operation to compile and execute correctly

Summary by CodeRabbit

• Bug Fixes

  • Recursive JIT calls now correctly handle functions returning no value, integers, booleans, and floating-point values.
  • Unsupported return shapes are reported clearly instead of being interpreted incorrectly.

• Tests

  • Added coverage for recursive boolean evaluation, including negation and base cases.
  • Added coverage for recursive floating-point calculations across multiple recursion levels.