mountainash-data: Add ClickHouse dialect to IbisBackend

[discreteds]

Summary

Add ClickHouse as a supported dialect in mountainash-data's IbisBackend, enabling IbisBackend(dialect="clickhouse", ...) connections.

Motivation

While building a PoC connecting mountainash to ClickHouse (via raw ibis.clickhouse.connect()), it became clear that the connection should go through mountainash-data's IbisBackend for consistency with the rest of the framework. ClickHouse is currently not one of the 12 registered dialects.

Scope

Follow the existing data-driven dialect registration pattern:

1. Settings class — ClickHouseAuthSettings in core/settings/clickhouse.py with a BackendDescriptor covering:

   • HOST, PORT (default 9000, or 443 for HTTPS/native), DATABASE
   • SECURE (bool, for TLS — common with cloud-hosted ClickHouse)
   • USER, PASSWORD (via PasswordAuth)

2. Dialect registration — DialectSpec entry in backends/ibis/dialects/_registry.py:

   • ibis_backend_name: "clickhouse"
   • connection_mode: KWARGS
   • connection_string_scheme: "clickhouse://"
   • connection_builder: maps settings to ibis.clickhouse.connect(**kwargs)

3. Optional dependency — ibis-framework[clickhouse] under a [clickhouse] extra in pyproject.toml

4. Constants — Add CLICKHOUSE to CONST_DB_PROVIDER_TYPE enum

Expected Usage

from mountainash_data import IbisBackend

# Dialect + kwargs
with IbisBackend(dialect="clickhouse", host="sql-clickhouse.clickhouse.com", port=443, user="demo", database="pypi", secure=True) as backend:
    tables = backend.list_tables()
    info = backend.inspect_table("pypi_downloads_per_day")

# URL form
with IbisBackend("clickhouse://demo@sql-clickhouse.clickhouse.com:443/pypi?secure=true") as backend:
    ...

# Settings-driven
params = SettingsParameters.create(
    settings_class=ClickHouseAuthSettings,
    HOST="sql-clickhouse.clickhouse.com",
    PORT=443,
    DATABASE="pypi",
    SECURE=True,
    auth=PasswordAuth(username="demo", password=""),
)
with IbisBackend(params) as backend:
    ...

Notes

• ibis-framework 12.0.0 supports ClickHouse via ibis.clickhouse.connect() with kwargs: host, port, user, password, database, secure
• No special DDL hooks needed initially (ClickHouse uses standard SQL for most operations)
• The existing PostgreSQL and MySQL dialect registrations are good templates to follow