ClickHouse virtual catalog is not stripped from CREATE TABLE AS SELECT / INSERT source queries (physical layer) #5960

Describe the bug

This is a sibling of #5938 / #5940 ("virtual catalog not stripped from CREATE VIEW source queries"). That fix covered create_view, but the same bug still exists on the physical-table path: _create_table (CTAS) and the INSERT paths strip the injected virtual catalog only from the target table name, not from the source query's FROM tables. As a result ClickHouse receives a 3-part identifier and fails with SYNTAX_ERROR (code 62) whenever a FULL (or incremental) model reads from another model.

Environment

• sqlmesh 0.236.1
• A ClickHouse gateway (catalog-unsupported) coexisting with a catalog-aware gateway (BigQuery) in the same project, so scheduler.get_default_catalog_per_gateway() injects a virtual catalog (__ch__) into the ClickHouse adapter.
• default_gateway: ch

Reproduction

config.yaml:

model_defaults:
  start: 2025-01-01
  dialect: clickhouse

gateways:
  ch:
    connection:
      type: clickhouse
      host: <host>
      username: <user>
      password: <pw>
    state_connection: { type: postgres, host: ..., port: 5432, user: ..., password: ..., database: sqlmesh }
  bigquery:                 # <-- merely defining a catalog-aware gateway triggers virtual-catalog injection
    connection:
      type: bigquery
      method: oauth
      project: my-project
      location: EU
    state_connection: { type: postgres, ... }

default_gateway: ch

models/silver/test_table.sql:

MODEL (name silver.test_table, kind FULL);
SELECT 1 AS first_column;

models/gold/test_table.sql:

MODEL (name gold.test_table, kind FULL);
SELECT *, 2 AS second_column FROM silver.test_table;

Run:

sqlmesh plan

Actual behaviour

"__ch__"."gold"."test_table"
  DatabaseError:
    Code: 62. DB::Exception: Syntax error: failed at position 512 (AS):
    AS "test_table") AS "_subquery". ... (SYNTAX_ERROR)
Error: Plan application failed.

The statement sent to ClickHouse for the physical gold table is:

CREATE TABLE "sqlmesh__gold"."gold__test_table__..." AS
SELECT ...
FROM "__ch__"."sqlmesh__silver"."silver__test_table__..." AS "test_table"   -- <-- 3-part FQN, invalid in ClickHouse

(The nested source table still carries __ch__; ClickHouse only supports database.table.)

Impact

Gateway-managed virtual-layer promotion cannot complete for ClickHouse models
in affected multi-gateway projects. Physical objects may be created before the
promotion failure, leaving a partially applied plan to clean up.

Environment

SQLMesh: 0.236.1
ClickHouse: 26.7