test: add FBIP and RC verification test cases

Add test cases demonstrating FBIP (Functional But In-Place) optimization:
- test_fbip_clean.lux: Basic FBIP chain (map, filter, reverse)
- test_fbip_allocs.lux: Single-owner allocation test with range/map/filter/reverse
- test_no_fbip.lux: Demonstrates shared reference forcing rc>1 path
- test_rc_comparison.lux: Comparison of FBIP vs non-FBIP allocations

All tests verify no memory leaks with the RC system.

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

examples/test_fbip_clean.lux

@@ -0,0 +1,9 @@
+fn main(): Unit = {
+    // Test FBIP without string operations
+    let nums = [1, 2, 3, 4, 5]
+    let doubled = List.map(nums, fn(x: Int): Int => x * 2)
+    let filtered = List.filter(doubled, fn(x: Int): Bool => x > 4)
+    let reversed = List.reverse(filtered)
+    let len = List.length(reversed)
+    Console.print("done")
+}