Add snapshot for Node.js/.NET getSessionMetadata E2E tests

The test harnesses derive the snapshot filename from the test name.
Node.js and .NET use 'should get session metadata by ID' which maps
to should_get_session_metadata_by_id.yaml, while Python/Go use a
slightly different name. Add the matching snapshot so the replay
proxy can serve responses in CI.

Author: MackinnonBuck

test/snapshots/session/should_get_session_metadata_by_id.yaml

@@ -0,0 +1,11 @@
+models:
+  - claude-sonnet-4.5
+conversations:
+  - messages:
+      - role: system
+        content: ${system}
+      - role: user
+        content: Say hello
+      - role: assistant
+        content: Hello! I'm GitHub Copilot CLI, ready to help you with your software engineering tasks. What can I assist you
+          with today?