dev-python/logfire is not in Gentoo, so make the logfire imports in the
test suite optional and deselect the tests that need its capfire fixture.

--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -15,7 +15,10 @@
 os.environ.setdefault("LOGFIRE_DISTRIBUTED_TRACING", "true")
 
 import opentelemetry.trace  # noqa: E402  (env var must be set before logfire import below)
-from logfire.testing import CaptureLogfire  # noqa: E402
+try:
+    from logfire.testing import CaptureLogfire  # noqa: E402
+except ImportError:
+    CaptureLogfire = None
 
 import mcp.shared._otel  # noqa: E402
 
--- a/tests/server/conftest.py
+++ b/tests/server/conftest.py
@@ -3,7 +3,11 @@
 from collections.abc import Iterator
 
 import pytest
-from logfire.testing import CaptureLogfire, TestExporter
+try:
+    from logfire.testing import CaptureLogfire, TestExporter
+except ImportError:
+    CaptureLogfire = None
+    TestExporter = None
 from opentelemetry.sdk.trace import ReadableSpan
 
 
--- a/tests/shared/test_otel.py
+++ b/tests/shared/test_otel.py
@@ -2,7 +2,10 @@
 
 import mcp_types as types
 import pytest
-from logfire.testing import CaptureLogfire
+try:
+    from logfire.testing import CaptureLogfire
+except ImportError:
+    CaptureLogfire = None
 from opentelemetry.trace import StatusCode
 
 from mcp.client.client import Client