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/.

_selfhost/src/parser.bux

@@ -1326,7 +1326,9 @@ func parserParseDecl(p: *Parser) -> *Decl {
         discard parserAdvance(p); // async
         return parserParseFuncDecl(p, isPublic, false, true);
     }
-    if kind == tkFunc { return parserParseFuncDecl(p, isPublic, false, false); }
+    if kind == tkFunc {
+        return parserParseFuncDecl(p, isPublic, false, false);
+    }
     if kind == tkStruct { return parserParseStructDecl(p, isPublic); }
     if kind == tkEnum { return parserParseEnumDecl(p, isPublic); }
     if kind == tkImport { return parserParseImportDecl(p, isPublic); }