feat(llvm): Complete function call system implementation by ChatGPT5

Major improvements to LLVM backend function call infrastructure:

## Key Changes

### Function Call System Complete
- All MIR functions now properly lowered to LLVM (not just entry)
- Function parameter binding to LLVM arguments implemented
- ny_main() wrapper added for proper entry point handling
- Callee resolution from ValueId to function symbols working

### Call Instruction Analysis
- MirInstruction::Call was implemented but system was incomplete
- Fixed "rhs missing" errors caused by undefined Call return values
- Function calls now properly return values through the system

### Code Modularization (Ongoing)
- BoxCall → instructions/boxcall.rs ✓
- ExternCall → instructions/externcall.rs ✓
- Call remains in mod.rs (to be refactored)

### Phase 21 Documentation
- Added comprehensive AI evaluation from Gemini and Codex
- Both AIs confirm academic paper potential for self-parsing AST DB approach
- "Code as Database" concept validated as novel contribution

Co-authored-by: ChatGPT5 <noreply@openai.com>

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/backend/llvm/compiler/codegen/instructions/externcall/mod.rs

@@ -0,0 +1,47 @@
+mod console;
+mod env;
+
+use std::collections::HashMap;
+
+use crate::backend::llvm::context::CodegenContext;
+use crate::mir::{function::MirFunction, ValueId};
+use inkwell::values::BasicValueEnum as BVE;
+
+/// Full ExternCall lowering dispatcher (console/debug/env.*)
+pub(in super::super) fn lower_externcall<'ctx>(
+    codegen: &CodegenContext<'ctx>,
+    func: &MirFunction,
+    vmap: &mut HashMap<ValueId, BVE<'ctx>>,
+    dst: &Option<ValueId>,
+    iface_name: &str,
+    method_name: &str,
+    args: &[ValueId],
+) -> Result<(), String> {
+    // console/debug
+    if (iface_name == "env.console"
+        && matches!(method_name, "log" | "warn" | "error"))
+        || (iface_name == "env.debug" && method_name == "trace")
+    {
+        return console::lower_log_or_trace(codegen, vmap, dst, iface_name, method_name, args);
+    }
+    if iface_name == "env.console" && method_name == "readLine" {
+        return console::lower_readline(codegen, vmap, dst, args);
+    }
+
+    // env.*
+    if iface_name == "env.future" && method_name == "spawn_instance" {
+        return env::lower_future_spawn_instance(codegen, vmap, dst, args);
+    }
+    if iface_name == "env.local" && method_name == "get" {
+        return env::lower_local_get(codegen, func, vmap, dst, args);
+    }
+    if iface_name == "env.box" && method_name == "new" {
+        return env::lower_box_new(codegen, vmap, dst, args);
+    }
+
+    Err(format!(
+        "ExternCall lowering unsupported: {}.{} (add a NyRT shim for this interface method)",
+        iface_name, method_name
+    ))
+}
+