feat: Add ClickHouse connector skill

[major-connector-creator]

Summary

Adds the AI Coder skill file for the ClickHouse database connector.

Changes

plugins/shared/skills/resources_clickhouse/SKILL.md (new)

Skill file following the MySQL skill pattern with YAML frontmatter (name: using-clickhouse-connector).

Content includes:

• Common section: Security, MCP tools pattern, TypeScript client generation, invocation key rules
• MCP Tools: clickhouse_query (read-only, no approval) and clickhouse_invoke (read/write, requires approval)
• TypeScript Client: Usage example with invoke<T>(sql, params?, invocationKey, timeoutMs?)
• Tips:
  • Use clickhouse_query exclusively for read-only operations
  • Uses positional ? placeholders
  • Default HTTP port is 8123, HTTPS is 8443
  • Default username is "default", default database is "default"
  • Schema exploration with SHOW DATABASES, SHOW TABLES, DESCRIBE TABLE, SHOW CREATE TABLE, EXISTS TABLE
  • ClickHouse is a columnar analytics DB — avoid SELECT * on large tables, use LIMIT
  • ClickHouse does NOT support UPDATE/DELETE on regular MergeTree tables — use ALTER TABLE ... UPDATE/DELETE for mutations
  • String comparison is case-sensitive by default; use lower() or ilike
  • Docs link: https://clickhouse.com/docs/en/sql-reference