test: Remove redundant comments from test files

Applies the same doc comment cleanup to test files:
- Removes test module headers (//! lines)
- Removes obvious test function comments
- Retains comments explaining non-obvious test scenarios

Test names should be descriptive enough to convey intent without
additional comments. Complex test setup or assertions that need
explanation retain their comments.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/fixture_tests.rs

@@ -1,5 +1,3 @@
-//! Tests for test fixtures - verifies they deserialize correctly.
-
 use lore::gitlab::types::{GitLabDiscussion, GitLabIssue};
 use serde::de::DeserializeOwned;
 use std::path::PathBuf;
@@ -38,14 +36,11 @@ fn fixture_gitlab_issues_page_deserializes() {
         "Need at least 3 issues for pagination tests"
     );
 
-    // Check first issue has labels
     assert!(!issues[0].labels.is_empty());
 
-    // Check second issue has null description and empty labels
     assert!(issues[1].description.is_none());
     assert!(issues[1].labels.is_empty());
 
-    // Check third issue has multiple labels
     assert!(issues[2].labels.len() >= 3);
 }
 
@@ -67,7 +62,6 @@ fn fixture_gitlab_discussions_page_deserializes() {
         "Need multiple discussions for testing"
     );
 
-    // Check we have both individual_note=true and individual_note=false
     let has_individual = discussions.iter().any(|d| d.individual_note);
     let has_threaded = discussions.iter().any(|d| !d.individual_note);
     assert!(