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/block-expansion.html

@@ -0,0 +1,5 @@
+<ul>
+  <li><a href="#">foo</a></li>
+  <li><a href="#">bar</a></li>
+</ul>
+<p>baz</p>