Connection, cluster and time window

Run this before any other altinity-expert-clickhouse-* skill. It produces the facts every later skill reuses: connection mode, cluster name (or single node), ClickHouse version, Keeper presence, time window.

Step 1: choose the connection mode

Check your available tools in this order and stop at the first match:

1. MCP mode: a tool whose name contains clickhouse and one of query, execute, sql (for example clickhouse_execute_query, mcp__clickhouse__execute_query). Send exactly one SQL statement per call. If several ClickHouse MCP servers exist, ask the user which one to use.
2. Exec mode: a shell tool plus clickhouse-client (or clickhouse client). Use only the connection flags the user provided (--host, --port, --user, --password, --secure); do not guess credentials from environment variables. Run one statement per invocation with --query "<statement>". Never use --queries-file or --multiquery.
3. Neither: stop and ask the user how to reach ClickHouse. Do not install software and do not write helper scripts.

Step 2: verify connectivity and collect header facts

Run this one statement. It works on a standalone server (no macro, no Keeper) and on a cluster: