feat: expose JIT compiler via CLI command

Add `lux compile <file>` command that compiles and runs Lux code using
the Cranelift JIT compiler. Includes --benchmark flag for timing.

- Add compile_file() function in main.rs
- Add jit_test.lux example with fib(30) + factorial(10)
- Update VISION.md status

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/jit_test.lux

@@ -0,0 +1,16 @@
+// Test file for JIT compilation
+// This uses only features the JIT supports: integers, arithmetic, conditionals, functions
+
+fn fib(n: Int): Int =
+    if n <= 1 then n
+    else fib(n - 1) + fib(n - 2)
+
+fn factorial(n: Int): Int =
+    if n <= 1 then 1
+    else n * factorial(n - 1)
+
+fn main(): Int = {
+    let a = fib(30)
+    let b = factorial(10)
+    a + b
+}