fix(clickhouse): strip virtual catalogs from executed queries and inserts - #6036

Summary

• Why this is necessary: SQLMesh uses a synthetic catalog to identify a gateway, but ClickHouse expects database.table names. Direct queries, including audit queries and INSERT post-statements used for initial history loads, bypass create_view normalization. Without this fix, otherwise valid SQL reaches ClickHouse with unsupported catalog-qualified table and column names and can fail during execution. Fixing the adapter avoids requiring each project to add its own rendering workaround.
• Strip the configured ClickHouse virtual catalog from table and qualified-column references when executing SELECT or INSERT expressions directly.
• For example, INSERT INTO __gw__.db.target SELECT ... FROM __gw__.db.source now reaches ClickHouse using db.target and db.source. Direct execution bypasses the view-creation handling added in fix(clickhouse): strip virtual catalog from view sources #5940; fix(clickhouse): initialize virtual catalog for cleanup #5941 addresses cleanup initialization separately.
• Preserve the caller’s expression, unrelated catalogs, and literal values. Existing create-view catalog validation remains intact.

Test Plan

• Reproduced failing INSERT and SELECT regressions before the fix; all 38 ClickHouse adapter tests pass after it.
• Covered target/source names, qualified columns, configured catalog fallback, expression immutability, and preservation of unrelated catalogs/literals.
• make style passes: Ruff, formatting, mypy, and migration checks.
• make fast-test passes: 2,625 tests passed and four skipped; all isolated, registry-isolation, and dialect-isolation suites passed.
• git diff --check passes.