fix: configure markdownlint-cli2 properly

- Wrap config in 'config' key for markdownlint-cli2
- Use MD013 rule name instead of 'line-length' alias
- Disable MD013 line-length checks
- Add allowed languages: sh, python, csv, tree
- Fix broken link reference in TODO.md
- All markdown linting now passes (37 errors -> 0)

package.json

@@ -6,7 +6,7 @@
     "lint:js": "oxlint",
     "lint:js:fix": "bun lint:js -- --fix",
     "lint:js:strict": "oxlint --import-plugin -D correctness -W suspicious",
-    "lint:md": "markdownlint-cli2 \"**/*.md\"",
+    "lint:md": "markdownlint-cli2 \"**/*.md\" \"#node_modules\" \"#.{node_modules,trunk,grit,venv}\"",
     "lint:md:fix": "bun lint:md -- --fix",
     "lint:py": "uvx ruff check",
     "lint:py:fix": "uvx ruff check --fix",
@@ -21,17 +21,5 @@
     "prettier": "^3.6.2",
     "prettier-plugin-jinja-template": "^2.1.0",
     "prettier-plugin-packagejson": "^2.5.19"
-  },
-  "markdownlint-cli2": {
-    "config": {
-      "MD013": false,
-      "MD033": false
-    },
-    "ignores": [
-      ".git",
-      ".trunk",
-      ".venv",
-      "node_modules"
-    ]
   }
 }