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/extends-not-top-level/index.test.js

@@ -0,0 +1,15 @@
+const pug = require('../../');
+
+// regression test for #2404
+
+test('extends not top level should throw an error', () => {
+  expect(() => pug.compileFile(__dirname + '/index.pug')).toThrow(
+    'Declaration of template inheritance ("extends") should be the first thing in the file. There can only be one extends statement per file.'
+  );
+});
+
+test('duplicate extends should throw an error', () => {
+  expect(() => pug.compileFile(__dirname + '/duplicate.pug')).toThrow(
+    'Declaration of template inheritance ("extends") should be the first thing in the file. There can only be one extends statement per file.'
+  );
+});