chore: initialize NexaCore compiler workspace with basic frontend and CLI

Add initial project structure for NexaCore programming language compiler:
- Create Cargo workspace with 4 crates (cli, driver, frontend, runtime)
- Add lexer with indentation-based tokenization and keyword support
- Add parser for modules, functions, structs, and basic expressions
- Implement CLI with build command and placeholder subcommands
- Add driver crate to orchestrate compilation pipeline
- Include .gitignore for Rust build

crates/nxc-cli/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "nxc-cli"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[[bin]]
+name = "nexacore"
+path = "src/main.rs"
+
+[dependencies]
+nxc-driver = { path = "../nxc-driver" }
+

crates/nxc-cli/src/main.rs

@@ -0,0 +1,65 @@
+use std::env;
+use std::path::Path;
+use std::process::ExitCode;
+
+fn main() -> ExitCode {
+    match run() {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(message) => {
+            eprintln!("{message}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn run() -> Result<(), String> {
+    let mut args = env::args().skip(1);
+    let Some(command) = args.next() else {
+        print_help();
+        return Ok(());
+    };
+
+    match command.as_str() {
+        "build" => {
+            let Some(path) = args.next() else {
+                return Err("usage: nexacore build <file.nx>".to_string());
+            };
+            let result = nxc_driver::compile_file(Path::new(&path))
+                .map_err(format_compile_error)?;
+            println!("compiled {path}");
+            println!("tokens: {}", result.tokens.len());
+            println!("items: {}", result.module.items.len());
+            Ok(())
+        }
+        "run" => Err("runtime execution is not implemented yet".to_string()),
+        "new" => Err("project scaffolding is not implemented yet".to_string()),
+        "test" => Err("test runner is not implemented yet".to_string()),
+        "fmt" => Err("formatter is not implemented yet".to_string()),
+        "add" => Err("package manager is not implemented yet".to_string()),
+        "doc" => Err("docs generator is not implemented yet".to_string()),
+        _ => Err(format!("unknown command: {command}")),
+    }
+}
+
+fn format_compile_error(error: nxc_driver::CompileError) -> String {
+    match error {
+        nxc_driver::CompileError::Io(io) => format!("io error: {io}"),
+        nxc_driver::CompileError::Parse(parse) => format!(
+            "parse error at line {}, column {}: {}",
+            parse.span.line, parse.span.column, parse.message
+        ),
+    }
+}
+
+fn print_help() {
+    println!("NexaCore CLI");
+    println!("usage:");
+    println!("  nexacore build <file.nx>");
+    println!("  nexacore run <file.nx>");
+    println!("  nexacore new <name>");
+    println!("  nexacore test");
+    println!("  nexacore fmt");
+    println!("  nexacore add <package>");
+    println!("  nexacore doc");
+}
+