fix(foundry): don't treat an env-derived resource as conflicting with base_url

[sean-kim05]

Summary

AnthropicFoundry.copy() / with_options() (and their async equivalents) raise

ValueError: base_url and resource are mutually exclusive

whenever ANTHROPIC_FOUNDRY_RESOURCE is set in the environment.

Root cause

copy() reconstructs the client and always forwards base_url (derived from the live client) while never forwarding resource:

return self.__class__(
    ...
    base_url=str(base_url or self.base_url),   # always non-None
    ...                                         # resource is never passed
)

__init__ then falls back to the env var for resource:

resource = resource if resource is not None else os.environ.get("ANTHROPIC_FOUNDRY_RESOURCE")
base_url = base_url if base_url is not None else os.environ.get("ANTHROPIC_FOUNDRY_BASE_URL")

if base_url is None:
    ...
elif resource is not None:
    raise ValueError("base_url and resource are mutually exclusive")

So when ANTHROPIC_FOUNDRY_RESOURCE is set, the forwarded base_url and the env-derived resource are both non-None and the guard fires — even though the caller never supplied a conflicting configuration. Any deployment that configures Foundry purely through env vars (ANTHROPIC_FOUNDRY_RESOURCE + ANTHROPIC_FOUNDRY_API_KEY) and then calls the public copy() / with_options() API hits this.

Reproduction

os.environ["ANTHROPIC_FOUNDRY_RESOURCE"] = "example-resource"
os.environ["ANTHROPIC_FOUNDRY_API_KEY"] = "sk-foundry-abc"
client = AnthropicFoundry()   # OK
client.copy()                 # ValueError: base_url and resource are mutually exclusive

Fix

An env-derived resource is only a fallback for building base_url, so it must not conflict with a base_url that was actually supplied. Track whether resource was passed explicitly and only raise on a genuine caller-supplied conflict; otherwise a supplied base_url wins over the resource env var (matching normal explicit-arg-over-env precedence). Applied symmetrically to the sync and async clients.

Explicitly passing both base_url and resource is still rejected (and remains a static type error via the existing overloads).

Testing

Added to tests/lib/test_azure.py:

• test_copy_with_resource_from_environment (sync + async) — copy() / with_options() succeed with ANTHROPIC_FOUNDRY_RESOURCE set (fails before this change).
• test_explicit_base_url_and_resource_conflict — the runtime guard still rejects an explicit base_url + resource pair.

Verified RED → GREEN. Full tests/lib/test_azure.py passes (21 tests); ./scripts/lint clean (ruff + pyright + mypy).