Every handler was wrapping its body in try/catch and returning fail(code,
error.message), leaking raw DB messages to the renderer and bypassing the
sanitizer in registerHandle. Removed the 14 inner try/catch shells so
errors surface through ipc-support's IPC_HANDLER_FAILED / IPC_INVALID_PAYLOAD
path. Also removed the duplicate emitEvent({ type: 'domain-changed' }) in
addThreadEvent — publishDomainChanged already emits the same event.
ZacharyZhang-NY