selfhost: trait bounds parsing, sema checks, and generic monomorphization fix

- AST: add typeParam0Bound/typeParam1Bound to Decl, strValue2 to dkImpl
- Parser: parse <T: Trait> bounds, Self type in interfaces, extend-for blocks
- Sema: add interfaceTable/methodTable, Sema_CheckTraitBounds, Sema_TypeImplements
- HIR lower: two-pass decl iteration — collect generic funcs before lowering bodies
  Fixes Max<Circle>(...) not generating Max_Circle when caller precedes callee
- C backend: skip generic funcs in emission (only emit monomorphized instances)
- Array.bux: fix for-loop over monomorphized Array types
- All debug prints removed; selfhost loop passes (C output IDENTICAL)

lib/Array.bux

@@ -30,6 +30,11 @@ func Array_Get<T>(self: *Array<T>, index: uint) -> T {
     return self.data[index];
 }
 
+func Array_Set<T>(self: *Array<T>, index: uint, value: T) {
+    bux_bounds_check(index, self.len);
+    self.data[index] = value;
+}
+
 func Array_Len<T>(self: *Array<T>) -> uint {
     return self.len;
 }