The name of Hermes' MCP callback for the codex app-server runtime was spelled
as a string literal in five places (the server itself, the runtime migration
that writes `[mcp_servers.hermes-tools]`, the Kanban worker override launcher,
the elicitation auto-accept handler, the display-name stripper and the switch
report) and had already drifted once (#111707). Define it once in
agent/transports/hermes_tools_mcp_server.py — the module that IS the server and
whose module-level imports are stdlib only, so every higher layer (transports,
agent/codex_runtime, hermes_cli) can import it without a cycle — and read it
everywhere.
Two invariant tests in tests/agent/transports/: the worker's `-c
mcp_servers.<name>.env.*` overrides only ever target an entry the migration
really writes to config.toml (red on the pre-fix base: `{'hermes-mcp'}`), and
non-owned launches emit no override at all.
Refs #111707
204f345816