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/escape-test.pug

@@ -0,0 +1,8 @@
+doctype html
+html
+    head
+        title escape-test
+    body
+        textarea
+            - var txt = '<param name="flashvars" value="a=&quot;value_a&quot;&b=&quot;value_b&quot;&c=3"/>'
+            | #{txt}