Rename MCP server identifier from state-hub to dev-hub

Introduce canonical MCP_SERVER_NAME constants, shared registration helpers,
and a migrate_mcp_config.py script for ~/.claude.json upgrades. Registration,
patch, and custodian CLI checks accept both dev-hub and legacy state-hub during
transition. API root metadata and session-protocol template reflect the new name.

custodian_cli.py

@@ -126,11 +126,9 @@ def _detect_domain(project_path: Path) -> str | None:
 
 
 def _check_mcp() -> bool:
-    claude_json = Path.home() / ".claude.json"
-    if not claude_json.exists():
-        return False
-    config = json.loads(claude_json.read_text())
-    return "state-hub" in config.get("mcpServers", {})
+    from scripts.mcp_registration import load_claude_json, mcp_server_registered
+
+    return mcp_server_registered(load_claude_json())
 
 
 # ── Subcommands ────────────────────────────────────────────────────────────────
@@ -193,7 +191,8 @@ def cmd_register(args: argparse.Namespace) -> None:
     if _check_mcp():
         print("    MCP OK")
     else:
-        print("WARNING: 'state-hub' not in ~/.claude.json.")
+        print("WARNING: 'dev-hub' (or legacy 'state-hub') not in ~/.claude.json.")
+        print("  Run: python scripts/migrate_mcp_config.py  # if upgrading legacy config")
         print("  See ~/.claude/CLAUDE.md → MCP Server Registration section.")
 
     # ── Step 5: Write CLAUDE.custodian.md ─────────────────────────────────────