Fix: create_external_models misclassifies cross-repo models as external #3603

Job	Run time
changes	6s
test-dbt-versions (1.6)	1m 36s
test-dbt-versions (1.7)	1m 43s
test-dbt-versions (1.5)	1m 37s
test-dbt-versions (1.10)	1m 44s
test-dbt-versions (1.8)	1m 41s
test-dbt-versions (1.3)	1m 38s
test-dbt-versions (1.9)	1m 36s
test-dbt-versions (1.4)	1m 30s
test-vscode	0s
test-vscode-e2e	-1s
cicd-tests-windows	12m 14s
migration-test	1m 36s
doc-tests	33s
style-and-cicd-tests (3.12)	24m 40s
style-and-cicd-tests (3.10)	24m 1s
engine-tests-docker (mssql)	1m 42s
style-and-cicd-tests (3.11)	23m 11s
engine-tests-docker (trino)	8m 8s
engine-tests-docker (mysql)	1m 41s
engine-tests-docker (risingwave)	2m 41s
style-and-cicd-tests (3.9)	19m 4s
style-and-cicd-tests (3.13)	24m 17s
engine-tests-docker (duckdb)	1m 42s
engine-tests-docker (spark)	5m 5s
engine-tests-docker (clickhouse)	3m 31s
engine-tests-docker (postgres)	2m 45s
ui-style	-1s
ui-test	-1s
engine-tests-cloud	-1s
	2h 49m 58s

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