fix(ci): duplicate comments prevented via issue id deduplication (#3449)

Linear sync created duplicate comments on issues when same ID appeared
in both PR body and branch name. Example: ENG-8061 got two identical
"Now available in stable release v0.30.4" comments 1 second apart.

Root cause: IssueIDs() extracted from both PR body AND branch name,
returning duplicates when both contained the same issue reference.
This was exposed by commit e480400 which added stable release comments
for already-released issues - before that, duplicates were silently
skipped because issue was already in "Released" state.

Resolves OPS-460

(cherry picked from commit cfcf45a)

# Conflicts:
#	hack/linear-sync/main.go
#	hack/linear-sync/main_test.go

Author: Piotr1215

hack/linear-sync/main.go

@@ -154,6 +154,10 @@ func run(
 		}
 	}
 
+	// Deduplicate issue IDs - same issue can appear in both PR body and branch name,
+	// or across multiple PRs referencing the same issue
+	releasedIssues = deduplicateIssueIDs(releasedIssues)
+
 	logger.Info("Found issues in pull requests", "count", len(releasedIssues))
 
 	linearClient := NewLinearClient(ctx, *linearToken)
@@ -189,4 +193,21 @@ func run(
 	logger.Info("Linear sync completed", "processed", len(releasedIssues), "released", releasedCount, "skipped", skippedCount)
 
 	return nil
-}
+<<<<<<< HEAD
+}
+=======
+}
+
+// deduplicateIssueIDs removes duplicate issue IDs from the slice while preserving order
+func deduplicateIssueIDs(issueIDs []string) []string {
+	seen := make(map[string]bool)
+	result := make([]string, 0, len(issueIDs))
+	for _, id := range issueIDs {
+		if !seen[id] {
+			seen[id] = true
+			result = append(result, id)
+		}
+	}
+	return result
+}
+>>>>>>> cfcf45a9d (fix(ci): duplicate comments prevented via issue id deduplication (#3449))