fix: add execution_environment to Cortex Analyst tool_resources (closes #5)

[Matts52]

Summary

• Adds the required execution_environment block (type: warehouse, warehouse) to the Analyst1 tool_resource example in the README, fixing the runtime error reported in Document cortex_search tool_resources schema: name/title_column/id_column and execution_environment #5.
• Updates integration_tests/models/agent_with_semantic_view.sql to include the same block, using the existing SNOWFLAKE_TEST_WAREHOUSE env var.
• The Cortex Search side (name, title_column, id_column) was already correct in both the README and integration tests; no changes were needed there.

Test plan

• Verify dbt compile on integration_tests/ renders execution_environment under OrdersAnalyst in the compiled YAML.
• Run integration tests against a Snowflake environment to confirm the agent_with_semantic_view model creates successfully.

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