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/sample_data/pug/test/cases/inheritance.alert-dialog.html

@@ -0,0 +1,6 @@
+<div class="window"><a class="close" href="#">Close</a>
+  <div class="dialog">
+    <h1>Alert!</h1>
+    <p>I'm an alert!</p>
+  </div>
+</div>