Add gitignore-claude template and wire into registration flows

Introduce scripts/project_rules/gitignore-claude.template with the fleet
pattern that tracks .claude/rules/ while ignoring machine-local Claude state.
ensure_gitignore_claude_rules.py applies it during statehub register,
register_project.sh, and update_agent_instruction_files fleet regen.

scripts/update_agent_instruction_files.py

@@ -12,6 +12,13 @@ from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
 TEMPLATE_DIR = ROOT / "scripts" / "project_rules"
+
+import sys
+
+if str(ROOT) not in sys.path:
+    sys.path.insert(0, str(ROOT))
+
+from scripts.ensure_gitignore_claude_rules import ensure_claude_gitignore  # noqa: E402
 API_BASE = "http://127.0.0.1:8000"
 HOME_ROOT = Path("/home/worsch")
 WP_FILE_RE = re.compile(r"^([A-Za-z][A-Za-z0-9-]*-WP)-\d+", re.IGNORECASE)
@@ -189,6 +196,8 @@ def update_repo(
     if not scope_path.exists():
         scope_path.write_text(render(scope_template, values), encoding="utf-8")
 
+    ensure_claude_gitignore(path / ".gitignore")
+
     rules_dir = path / ".claude" / "rules"
     rules_dir.mkdir(parents=True, exist_ok=True)
     for name, template in rule_templates.items():