fix(mcp): unbounded elicitation mpsc channel allows memory exhaustion #2524
Description
Context
Added in #2521. The elicitation_tx channel in McpClient is unbounded (tokio::sync::mpsc::unbounded_channel). A malicious or misbehaving MCP server can flood elicitation requests, exhausting memory.
Required work
- Replace with a bounded channel (e.g., capacity 16)
- On send failure (channel full): log a warning and auto-decline the request server-side
- Config:
[mcp] elicitation_queue_capacity = 16(optional)