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/plugins.test.js

@@ -0,0 +1,18 @@
+const pug = require('../');
+
+test('#3295 - lexer plugins should be used in tag interpolation', () => {
+  const lex = {
+    advance(lexer) {
+      if ('~' === lexer.input.charAt(0)) {
+        lexer.tokens.push(lexer.tok('text', 'twiddle-dee-dee'));
+        lexer.consume(1);
+        lexer.incrementColumn(1);
+        return true;
+      }
+    },
+  };
+  const input = 'p Look at #[~]';
+  const expected = '<p>Look at twiddle-dee-dee</p>';
+  const output = pug.render(input, {plugins: [{lex}]});
+  expect(output).toEqual(expected);
+});