stdlib beginnings (heap alloc)

TODO.md

@@ -620,10 +620,13 @@
     byte slice when possible, and `[;0]u8` slices can decay to immutable `*c_char`/`?*c_char`
     parameters
 
-25. dynamic heap allocation
-  - see below for direction
-  - notes below are too big in scope for a first pass and the language is not mature enough to support it yet
-  - this first pass should focus on just basic heap allocation, so we have something to work with
+25. dynamic heap allocation (implemented; v1)
+  - `std/mem/heap` is a tiny relative-importable package over libc `malloc`/`free`
+  - `heap.alloc(size usize) ?*mut u8` returns nullable mutable byte memory; callers use existing optional unwraps
+  - `heap.free(ptr ?*mut u8) void` forwards to C `free`, including `none` / null
+  - typed allocation, allocator parameters, arenas/pools, build-mode heap policy, and escaping-allocation diagnostics remain deferred
+
+26. comptime polymorphism (zig inspired)
 
 ## A word on multi-unwrap