refactor: restructure CLI into library crate and add semantic analysis phase

Restructure nxc-cli crate:
- Extract main logic into lib.rs with main_entry() function
- Move nexacore binary to separate bin/nexacore.rs file
- Keep nxc binary in main.rs as thin wrapper

Add semantic analysis to compilation pipeline:
- Implement semantic analyzer with type checking and name resolution
- Add Type enum with Int, Float, Bool, String, Void, Struct, Function, Error variants
- Add typed AST nodes (TypedModule, TypedFunction

crates/nxc-driver/src/lib.rs

@@ -3,7 +3,8 @@ use std::fs;
 use std::path::{Path, PathBuf};
 
 use nxc_frontend::{
-    has_errors, Diagnostic, Item, LexResult, Lexer, Module, ParseResult, Parser, Token,
+    analyze, has_errors, Diagnostic, Item, LexResult, Lexer, Module, ParseResult, Parser, Token,
+    TypedModule,
 };
 
 #[derive(Debug, Clone)]
@@ -12,6 +13,7 @@ pub struct FrontendOutput {
     pub source: String,
     pub tokens: Vec<Token>,
     pub module: Module,
+    pub typed_module: Option<TypedModule>,
     pub diagnostics: Vec<Diagnostic>,
 }
 
@@ -86,13 +88,20 @@ pub fn check_source(path: PathBuf, source: String) -> FrontendOutput {
     } = Parser::new(tokens.clone()).parse_module();
 
     lexer_diagnostics.extend(parser_diagnostics);
+    let mut typed_module = None;
+
+    if !has_errors(&lexer_diagnostics) {
+        let semantic = analyze(&module);
+        lexer_diagnostics.extend(semantic.diagnostics);
+        typed_module = Some(semantic.module);
+    }
 
     FrontendOutput {
         path,
         source,
         tokens,
         module,
+        typed_module,
         diagnostics: lexer_diagnostics,
     }
 }
-