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-linker/test/errors/unexpected-block.input.json

@@ -0,0 +1,58 @@
+{
+  "type": "Block",
+  "nodes": [
+    {
+      "type": "Extends",
+      "file": {
+        "type": "FileReference",
+        "path": "../fixtures/empty.pug",
+        "line": 1,
+        "filename": "unexpected-block.pug",
+        "fullPath": "../fixtures/empty.pug",
+        "str": "",
+        "ast": {
+          "type": "Block",
+          "nodes": [],
+          "line": 0,
+          "filename": "../fixtures/empty.pug"
+        }
+      },
+      "line": 1,
+      "filename": "unexpected-block.pug"
+    },
+    {
+      "type": "NamedBlock",
+      "nodes": [
+        {
+          "type": "Tag",
+          "name": "div",
+          "selfClosing": false,
+          "block": {
+            "type": "Block",
+            "nodes": [
+              {
+                "type": "Text",
+                "val": "Hello World",
+                "line": 4,
+                "filename": "unexpected-block.pug"
+              }
+            ],
+            "line": 4,
+            "filename": "unexpected-block.pug"
+          },
+          "attrs": [],
+          "attributeBlocks": [],
+          "isInline": false,
+          "line": 4,
+          "filename": "unexpected-block.pug"
+        }
+      ],
+      "line": 3,
+      "filename": "unexpected-block.pug",
+      "name": "foo",
+      "mode": "replace"
+    }
+  ],
+  "line": 0,
+  "filename": "unexpected-block.pug"
+}