fix: drop PyYAML dep so verify job pytest passes

Store doc rules in bin/docs_rules.json (stdlib json). test_check_docs no
longer fails in the simulator job that only installs simulator/requirements.txt.

bin/check_docs.py

@@ -4,17 +4,13 @@
 from __future__ import annotations
 
 import argparse
+import json
 import re
 import sys
 from pathlib import Path
 
-try:
-    import yaml
-except ImportError:  # pragma: no cover - stdlib fallback for minimal envs
-    yaml = None  # type: ignore[assignment]
-
 ROOT = Path(__file__).resolve().parents[1]
-RULES_PATH = Path(__file__).with_name("docs_rules.yaml")
+RULES_PATH = Path(__file__).with_name("docs_rules.json")
 
 LINK_RE = re.compile(r"!?\[[^\]]*\]\(([^)]+)\)")
 BARE_SEE_RE = re.compile(r"(?<![\[(/])see\s+(\d{2})(?![\w-])", re.IGNORECASE)
@@ -22,10 +18,7 @@ SKIP_SCHEMES = ("http://", "https://", "mailto:", "tel:", "#")
 
 
 def load_rules(path: Path = RULES_PATH) -> dict:
-    text = path.read_text(encoding="utf-8")
-    if yaml is not None:
-        return yaml.safe_load(text)
-    raise RuntimeError("PyYAML is required to load docs_rules.yaml")
+    return json.loads(path.read_text(encoding="utf-8"))
 
 
 def slug_heading(text: str) -> str: