Support custom dbt profiles.yml path (DBT_PROFILES_DIR + project-local)

[anandgupta42]

Problem

The /discover command only finds profiles.yml at ~/.dbt/profiles.yml. Teams that keep profiles.yml in their project repo (common for CI/CD) or use DBT_PROFILES_DIR cannot have their profiles auto-discovered.

Expected behavior

Support dbt's standard resolution order:

1. Explicit path (tool parameter)
2. DBT_PROFILES_DIR environment variable
3. Project-local profiles.yml (next to dbt_project.yml)
4. ~/.dbt/profiles.yml (default fallback)

Context

Reported by user Garrett McClintock: "Is there a way to point to a different dbt profile path rather than ~/.dbt/profiles.yml? Ours is in our project repo, but discover is only finding the global one."