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/cases/include-with-text-head.input.json

@@ -0,0 +1,53 @@
+{
+  "type": "Block",
+  "nodes": [
+    {
+      "type": "Tag",
+      "name": "head",
+      "selfClosing": false,
+      "block": {
+        "type": "Block",
+        "nodes": [
+          {
+            "type": "Tag",
+            "name": "script",
+            "selfClosing": false,
+            "block": {
+              "type": "Block",
+              "nodes": [
+                {
+                  "type": "Text",
+                  "val": "alert('hello world');",
+                  "line": 3
+                }
+              ],
+              "line": 2,
+              "filename": "include-with-text-head.pug"
+            },
+            "attrs": [
+              {
+                "name": "type",
+                "val": "'text/javascript'",
+                "mustEscape": true
+              }
+            ],
+            "attributeBlocks": [],
+            "isInline": false,
+            "line": 2,
+            "filename": "include-with-text-head.pug",
+            "textOnly": true
+          }
+        ],
+        "line": 1,
+        "filename": "include-with-text-head.pug"
+      },
+      "attrs": [],
+      "attributeBlocks": [],
+      "isInline": false,
+      "line": 1,
+      "filename": "include-with-text-head.pug"
+    }
+  ],
+  "line": 0,
+  "filename": "include-with-text-head.pug"
+}