Fix TestFindJSONLPathDefault to expect beads.jsonl

Updates test and documentation to reflect the intentional change from
issues.jsonl to beads.jsonl (commit 7b865eb from Nov 20, 2025).

Fixes GH #356

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

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

internal/beads/beads_test.go

@@ -168,9 +168,9 @@ func TestFindJSONLPathDefault(t *testing.T) {
 	// Create a fake database path (no .jsonl files exist)
 	dbPath := filepath.Join(tmpDir, "test.db")
 
-	// Should return default issues.jsonl
+	// Should return default beads.jsonl
 	result := FindJSONLPath(dbPath)
-	expected := filepath.Join(tmpDir, "issues.jsonl")
+	expected := filepath.Join(tmpDir, "beads.jsonl")
 	if result != expected {
 		t.Errorf("Expected '%s', got '%s'", expected, result)
 	}