An agent with no matrix account has no `mcp__matrix__*` tools, so a
refusal that only says "use the matrix MCP tools" points it at something
it cannot call. `OPERATOR_SEND_REFUSAL` now names matrix for an agent
that has it, and tells one without it that there is no direct channel:
the operator reads its `set_status` line, its turn output on the
dashboard, and its logs. The allow-list refusal, the `send` tool
description, the MCP server instructions and the system prompt say
"over matrix if you have it" to match, and the helper-event bullets go
back to "ask the operator" without naming a channel.