fix: escape sequences in strings, --version/--help, manifest parser, debug cleanup

- Lexer (Nim + Bux): resolve escape sequences (\n, \t, \r, etc) instead of
  keeping raw source text in token. This was the root cause of \n being
  double-escaped to \\n in generated C code.
- Manifest parser (src_bux/manifest.bux): use bux_strlen instead of broken
  String_SplitCount(s, "") hack for string length; fix quote stripping.
- CLI (src_bux/cli.bux): --version/--help now recognized alongside version/help.
- Remove ~30+ debug Print statements from cli, parser, lexer, sema, main.
- Clean up unneeded Print/PrintInt extern declarations.
- _selfhost/src/: synced from src_bux/.

src_bux/main.bux

@@ -4,15 +4,13 @@ module Main {
 // C runtime for command-line args
 extern func bux_argc() -> int;
 extern func bux_argv(index: int) -> String;
+extern func bux_alloc(size: uint) -> *void;
 
 // Forward declaration from Cli module
 func Cli_Run(args: *String, argCount: int) -> int;
 
 func Main() -> int {
     let count: int = bux_argc();
-    Print("Main count=");
-    PrintInt(count);
-    PrintLine("");
     // Allocate array of String pointers
     let args: *String = bux_alloc(count as uint * 8) as *String;
     var i: int = 0;