style: clear clippy warnings from the stealth/adaptive work

- snapshot: make collect_fingerprints private (TreeNode is private, so a
  pub(super) fn leaked a more-private type)
- adaptive: if-let instead of single-arm match in attr_score
- stealth: move timezone test module to end of file (items-after-test-module)

No behavior change. Pre-release cleanup.

cli/src/native/snapshot.rs

@@ -226,7 +226,7 @@ fn build_ax_fingerprint(tree_nodes: &[TreeNode], idx: usize) -> ElementFingerpri
 /// Collect AX fingerprints for every node that has a backend node id, used as the
 /// candidate set when relocating a stale @ref. Reuses the same extraction as the
 /// baseline so the two are scored in the same space.
-pub(super) fn collect_fingerprints(tree_nodes: &[TreeNode]) -> Vec<(i64, ElementFingerprint)> {
+fn collect_fingerprints(tree_nodes: &[TreeNode]) -> Vec<(i64, ElementFingerprint)> {
     tree_nodes
         .iter()
         .enumerate()