fix: add scoped error logging for lexer/parser errors

- Add std.log.scoped(.pugz) to template.zig and view_engine.zig
- Log detailed error info (code, line, column, message) when parsing fails
- Log template path context in ViewEngine on parse errors
- Remove debug print from lexer, use proper scoped logging instead
- Move benchmarks, docs, examples, playground, tests out of src/ to project root
- Update build.zig and documentation paths accordingly
- Bump version to 0.3.1

tests/check_list/interpolation.escape.pug

@@ -0,0 +1,7 @@
+
+- var id = 42;
+foo
+  | some
+  | \#{text}
+  | here
+  | My ID #{"is {" + id + "}"}