refactor: keep pseudocode signatures, single call-marshalling path

emitPrototype now records each FUNCTION/PROCEDURE's pseudocode signature
(FuncSig: return type + per-param type/BYREF flag). CodeGen::
marshalCallArgs replaces the two verbatim-duplicated marshalling blocks
and dispatches on the declared signature instead of inferring BYREF from
pointer-typed LLVM params: BYVAL STRING params now receive the string
data pointer (no more runtime garbage), and BYVAL args are coerced to
the declared type (INTEGER->REAL args no longer emit invalid IR).

Top-level prototypes are pre-registered in compile(), so calls may
precede definitions; GenerateCall no longer fabricates i64 externs for
unknown names - an unregistered callee is a compile error. OUTPUT
reports an error when it cannot infer the expression type instead of
printing with the INTEGER format.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

1 files changed, 9 insertions, 10 deletions

diff --git a/AGENTS/CONVENTIONS.md b/AGENTS/CONVENTIONS.md
index c05734f..e09b6ee 100644
--- a/AGENTS/CONVENTIONS.md
+++ b/AGENTS/CONVENTIONS.md
@@ -58,16 +58,15 @@ non-zero when any flag is set. The parser still drops a failed statement, skips
 token, and continues — later statements can be swallowed during recovery, but the
 failure is always diagnosed and reflected in the exit code.
 
-**BYREF is a pointer-typed parameter, inferred structurally at call sites.**
-`FunctionGen` emits pointer params for BYREF; call sites (in CodeGen, duplicated for
-call-expr and call-stmt) treat *any* pointer-typed callee param as BYREF and require the
-argument to be a bare variable whose alloca is passed. The callee side, however, binds
-by the *declared* flag. Since STRING itself lowers to `ptr`, the two sides disagree for
-STRING: the caller always passes the alloca, but a declared-BYVAL STRING param (the
-default) copies that alloca *address* and treats it as the string data pointer — reading
-garbage at runtime. Only declared-BYREF STRING parameters work, and STRING arguments can
-never be literals/expressions. Function names get no mangling — a pseudocode
-`FUNCTION printf` collides with libc.
+**Calls dispatch on the declared signature.** `FunctionGen::emitPrototype` records every
+function's pseudocode signature (`FuncSig`: return type name + per-param type name and
+BYREF flag); `CodeGen::marshalCallArgs` — the single call-marshalling path for both
+call-expr and call-stmt — requires BYREF arguments to be bare variables (their alloca is
+passed) and coerces BYVAL arguments to the declared parameter type. STRING works on both
+sides in both modes. Top-level prototypes are pre-registered before statement emission,
+so call-before-definition is fine; a call with no registered signature is a compile
+error. Function names get no mangling — a pseudocode `FUNCTION printf` collides with
+libc.
 
 **Builtins are plain identifiers backed by one table.** All 11 builtins
 (LENGTH/MID/RIGHT/LEFT/LCASE/UCASE/ASC/CHR/IS_NUM/NUM_TO_STR/STR_TO_NUM) parse as