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.

scripts/migrate_mcp_config.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+"""Rename legacy state-hub MCP registration to dev-hub in ~/.claude.json."""
+from __future__ import annotations
+
+import json
+import shutil
+from datetime import datetime, timezone
+from pathlib import Path
+
+from mcp_server.constants import LEGACY_MCP_SERVER_NAME, MCP_SERVER_NAME
+
+CLAUDE_JSON = Path.home() / ".claude.json"
+
+
+def migrate_config(config: dict) -> tuple[dict, bool]:
+    servers = config.setdefault("mcpServers", {})
+    if MCP_SERVER_NAME in servers:
+        return config, False
+    if LEGACY_MCP_SERVER_NAME not in servers:
+        return config, False
+    servers[MCP_SERVER_NAME] = servers.pop(LEGACY_MCP_SERVER_NAME)
+    return config, True
+
+
+def main() -> None:
+    if not CLAUDE_JSON.exists():
+        print(f"ERROR: {CLAUDE_JSON} not found.")
+        raise SystemExit(1)
+
+    config = json.loads(CLAUDE_JSON.read_text())
+    migrated_config, changed = migrate_config(config)
+    if not changed:
+        if MCP_SERVER_NAME in config.get("mcpServers", {}):
+            print(f"OK: '{MCP_SERVER_NAME}' already registered.")
+        else:
+            print(
+                f"Nothing to migrate: neither '{LEGACY_MCP_SERVER_NAME}' nor "
+                f"'{MCP_SERVER_NAME}' found in mcpServers."
+            )
+        return
+
+    stamp = datetime.now(tz=timezone.utc).strftime("%Y%m%dT%H%M%SZ")
+    backup = CLAUDE_JSON.with_name(f".claude.json.bak-{stamp}")
+    shutil.copy2(CLAUDE_JSON, backup)
+    CLAUDE_JSON.write_text(json.dumps(migrated_config, indent=2) + "\n")
+    print(f"Backed up: {backup}")
+    print(f"Migrated: mcpServers['{LEGACY_MCP_SERVER_NAME}'] → mcpServers['{MCP_SERVER_NAME}']")
+
+
+if __name__ == "__main__":
+    main()