Structs, arrays, owned strings, memory model, modules, debug info

- struct with default values; constructors Point(1, 2) / Point(x: 1); field access, auto-deref through pointers
- []T arrays with bounds checks, literals, for-each, push/pop/insert/remove/clear/resize/find/contains/join/slice/reverse/sort
- str carries its length: .len, s[i], +, comparison, sub/find/split/trim/upper/lower/replace/repeat/bytes, str(x), int(s), float(s)
- Memory: values own their memory and are freed at the end of their block; assignment copies, temporaries move;
  parameters are lent and only copied when the function changes them; defer; new()/free() for manual heap memory
- input(), read_file/write_file/file_exists, exit(), fn main([]str args)
- Finch modules: import name, module.fn(), module.Struct
- C structs from headers (fields, fixed arrays, nested); passed and returned by value with the System V x86-64 ABI;
  addr(fn) gives C a callback
- link "file.c" compiles and links your own C code
- -g emits DWARF debug info (gdb/lldb)
- Small C runtime (runtime/finch_rt.c) embedded in the compiler, cached in ~/.cache/finch
- Tests: 58, all clean under valgrind (MEMCHECK=1 tests/run.sh)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/run/structs_arrays_strings.out

@@ -0,0 +1,18 @@
+Point(x: 1, y: 2) 1 2
+Point(x: 11, y: 2)
+Player(name: "Ola", pos: Point(x: 0, y: 0), scores: [], lives: 3)
+Ola 3 [10, 20] Point(x: 5, y: 0)
+Ola 2 Tom 3
+[10, 20] [10, 20, 99]
+[1, 3, 5, 8] 17 4
+8 [1, 3, 5]
+[42, 3, 5] false 1
+["a", "b", "c"] a-b-c
+Hello, Finch 12 H HELLO, FINCH Hello
+["a", "b", "", "c"] 4
+trim xxx aBBc true
+42! 3.5 true 124 5
+Jello, Finch
+h
+i
+[[1, 2], [3, 4, 5]] 5