[Feature]: MCP HTTP: make the session cap (100) and idle TTL (30 min) configurable #2283

Version: 0.87.7 (also 0.86.18; code unchanged on main)

What happens
packages/server/src/mcp-http.ts uses maxSessions = opts.maxSessions ?? 100 and sessionTtlMs = opts.sessionTtlMs ?? 30 * 60 * 1000. Nothing in the project config or environment reaches these options, so a project-bound HTTP server always caps at 100 sessions.

We run one ok start --only server on a Linux host for three long-running agents (two MCP clients plus short-lived scripts). Some clients open a new session per task and never send DELETE /mcp. Within a busy day the server reached 100 sessions. From then on every new initialize got 503 Too many active MCP sessions until idle sessions expired, so all agents lost TX access for up to 30 minutes. The server is still healthy at that point.

Ask (any one would solve it)

1. A config key or env var for maxSessions and sessionTtlMs.
2. When the cap is hit, evict the least-recently-used idle session instead of refusing the new one.
3. At minimum, document the cap and the 30-minute TTL in the MCP reference, so client authors know to send DELETE.