fix(deps): exclude relates-to from cycle detection (fixes #661)

relates-to dependencies are intentionally bidirectional ("see also" links)
and should not be reported as cycles by bd dep cycles. This matches the
existing behavior in AddDependency which already skips cycle prevention
for relates-to.

Changes:
- Filter relates-to edges in DetectCycles SQL query
- Add tests for relates-to exclusion from cycle detection
- Update existing test to reflect correct behavior

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/storage/sqlite/dependencies_test.go

@@ -1527,9 +1527,10 @@ func TestDetectCycles_MultipleGraphs(t *testing.T) {
 	}
 }
 
-// TestDetectCycles_RelatedTypeAllowsAdditionButReportsDetection tests relates-to allows bidirectional links
-// even though they're technically cycles. The cycle prevention only skips relates-to during AddDependency.
-func TestDetectCycles_RelatedTypeAllowsAdditionButReportsDetection(t *testing.T) {
+// TestDetectCycles_RelatesTypeAllowsBidirectionalWithoutCycleReport tests relates-to allows bidirectional links
+// and DetectCycles correctly excludes them (they're "see also" links, not problematic cycles).
+// This was fixed in GH#661 - relates-to is explicitly excluded from cycle detection.
+func TestDetectCycles_RelatesTypeAllowsBidirectionalWithoutCycleReport(t *testing.T) {
 	store, cleanup := setupTestDB(t)
 	defer cleanup()
 
@@ -1552,7 +1553,7 @@ func TestDetectCycles_RelatedTypeAllowsAdditionButReportsDetection(t *testing.T)
 		t.Fatalf("AddDependency for relates-to failed: %v", err)
 	}
 
-	// Add B relates-to A (this should succeed despite creating a cycle because relates-to skips cycle detection)
+	// Add B relates-to A (this should succeed - relates-to skips cycle prevention)
 	err = store.AddDependency(ctx, &types.Dependency{
 		IssueID:     issueB.ID,
 		DependsOnID: issueA.ID,
@@ -1562,15 +1563,16 @@ func TestDetectCycles_RelatedTypeAllowsAdditionButReportsDetection(t *testing.T)
 		t.Fatalf("AddDependency for reverse relates-to failed: %v", err)
 	}
 
-	// DetectCycles will report the cycle even though AddDependency allowed it
+	// DetectCycles should NOT report relates-to as cycles (GH#661 fix)
+	// relates-to is inherently bidirectional ("see also") and doesn't affect work ordering
 	cycles, err := store.DetectCycles(ctx)
 	if err != nil {
 		t.Fatalf("DetectCycles failed: %v", err)
 	}
 
-	// Relates-to bidirectional creates cycles (may report multiple entry points for same cycle)
-	if len(cycles) == 0 {
-		t.Error("Expected at least 1 cycle detected for bidirectional relates-to")
+	// relates-to bidirectional should NOT be reported as a cycle
+	if len(cycles) != 0 {
+		t.Errorf("Expected 0 cycles for bidirectional relates-to (GH#661 fix), got %d", len(cycles))
 	}
 
 	// Verify both directions exist