[Bug] dbt-loom does not inject models appropriately for unit tests to function.

[nicholasyager]

Describe the bug

If a unit test is created in a downstream project, and the test references a model in another project, dbt-core will yield a Compilation Error.

To Reproduce
Steps to reproduce the behavior:

1. In the customer_success test project, add a unit test to customers.

   unit_tests:
    - name: test_customer_type_mapping
      description: >
        Confirm that customer types are mapped corrected based on repeat buying behavior.
      model: customers
      given:
        - input: ref('stg_customers')
          rows:
            - { customer_id: 1, foo: "bar" }
   
        - input: ref('orders')
          rows:
            - {
                customer_id: 1,
                ordered_at: "2024-01-01T00:00:00Z",
                subtotal: 1.50,
                order_total: 5.50,
              }
            - {
                customer_id: 1,
                ordered_at: "2024-01-02T00:00:00Z",
                subtotal: 2.00,
                order_total: 5.50,
              }
   
      expect:
        rows:
          - {
              customer_id: 1,
              foo: "bar",
              count_lifetime_orders: 2,
              customer_type: "returning",
            }

2. In customer_success, run dbt build
3. See the following error.

dbt-loom-py3.12> $ dbt build                                                                                                                                                                                                                                                                                                                                                                                                                                                          [±main ●(✹)]
12:59:41  Running with dbt=1.8.0
12:59:41  Initializing dbt-loom=0.5.2
12:59:41  dbt-loom: Patching ref protection methods to support dbt-loom dependencies.
12:59:41  dbt-loom: Loading manifest for `revenue` from `file`
12:59:41  Registered adapter: duckdb=1.8.0
12:59:41  dbt-loom: Injecting nodes
12:59:41  [WARNING]: Model orders.v1 has passed its deprecation date of 2024-01-01T00:00:00-05:00. This model should be disabled or removed.
12:59:41  Found 13 models, 5 data tests, 1 source, 519 macros, 1 unit test
12:59:41  
12:59:42  Concurrency: 4 threads (target='dev')
12:59:42  
12:59:42  1 of 8 START sql view model main.stg_customers ................................. [RUN]
12:59:42  1 of 8 OK created sql view model main.stg_customers ............................ [OK in 0.07s]
12:59:42  2 of 8 START test not_null_stg_customers_customer_id ........................... [RUN]
12:59:42  3 of 8 START test unique_stg_customers_customer_id ............................. [RUN]
12:59:42  3 of 8 PASS unique_stg_customers_customer_id ................................... [PASS in 0.06s]
12:59:42  2 of 8 PASS not_null_stg_customers_customer_id ................................. [PASS in 0.07s]
12:59:42  4 of 8 START unit_test customers::test_customer_type_mapping ................... [RUN]
12:59:42  4 of 8 ERROR customers::test_customer_type_mapping ............................. [ERROR in 0.03s]
12:59:42  5 of 8 SKIP relation main.customers ............................................ [SKIP]
12:59:42  6 of 8 SKIP test accepted_values_customers_customer_type__new__returning ....... [SKIP]
12:59:42  7 of 8 SKIP test not_null_customers_customer_id ................................ [SKIP]
12:59:42  8 of 8 SKIP test unique_customers_customer_id .................................. [SKIP]
12:59:42  
12:59:42  Finished running 1 view model, 5 data tests, 1 unit test, 1 table model in 0 hours 0 minutes and 0.31 seconds (0.31s).
12:59:42  
12:59:42  Completed with 1 error and 0 warnings:
12:59:42  
12:59:42    Compilation Error in unit_test test_customer_type_mapping (models/marts/__models.yml)
  Unit_Test 'unit_test.customer_success.customers.test_customer_type_mapping' (models/marts/__models.yml) depends on a node named 'orders' in package or project 'revenue' which was not found
12:59:42  
12:59:42  Done. PASS=3 WARN=0 ERROR=1 SKIP=4 TOTAL=8

Expected behavior
A clear and concise description of what you expected to happen.

dbt-loom should inject dependencies early enough in the process to allow unit tests to leverage injected models.

Screenshots
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• OS: MacOS 14.5
• dbt-loom Version: 0.5.7
• dbt-core Version: 1.8.0

Additional context
Add any other context about the problem here.