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-lexer/cases/attrs.pug

@@ -0,0 +1,43 @@
+a(href='/contact') contact
+a(href='/save').button save
+a(foo, bar, baz)
+a(foo='foo, bar, baz', bar=1)
+a(foo='((foo))', bar= (1) ? 1 : 0 )
+select
+  option(value='foo', selected) Foo
+  option(selected, value='bar') Bar
+a(foo="class:")
+input(pattern='\\S+')
+
+a(href='/contact') contact
+a(href='/save').button save
+a(foo bar baz)
+a(foo='foo, bar, baz' bar=1)
+a(foo='((foo))' bar= (1) ? 1 : 0 )
+select
+  option(value='foo' selected) Foo
+  option(selected value='bar') Bar
+a(foo="class:")
+input(pattern='\\S+')
+foo(terse="true")
+foo(date=new Date(0))
+
+foo(abc
+   ,def)
+foo(abc,
+    def)
+foo(abc,
+		def)
+foo(abc
+		,def)
+foo(abc
+		def)
+foo(abc
+    def)
+
+- var attrs = {foo: 'bar', bar: '<baz>'}
+
+div&attributes(attrs)
+
+a(foo='foo' "bar"="bar")
+a(foo='foo' 'bar'='bar')