feat(adaptive): relocate stale @refs by AX fingerprint similarity

Borrow Scrapling's adaptive element finding, adapted to this project's
in-session AX-ref model. When a saved @ref's node is gone (or its identity
no longer matches) and the role/name/nth re-query also fails, score the
current page's candidate elements against an AX fingerprint captured at
snapshot time and relocate to the best match.

- New `adaptive` module: pure, browser-free scoring (role, accessible name
  via Levenshtein, AX properties, ancestor-role LCS, parent/sibling) plus
  pick_best with a high absolute threshold (0.70) AND a clear margin (0.15)
  over the runner-up — so ambiguous twins are refused rather than mis-clicked,
  matching the existing "fail loudly over wrong click" posture.
- Fingerprint captured during the existing AX-tree snapshot walk — no extra
  CDP round-trips. TreeNode is AX-only (no DOM tag/attrs), so we use AX role
  as the type and a few discriminating AX properties (value/url/level/checked);
  DOM id/class would have cost an N×describeNode storm per snapshot.
- Wired into both resolve_element_center and resolve_element_object_id: on a
  verify-identity mismatch or a stale-node fallback miss, relocation is tried
  before erroring. A confident match overrides the identity guard; otherwise
  the original error is surfaced. Opt out with AGENT_BROWSER_ADAPTIVE_REF=0.

README documents the new tuning knobs. Adds 9 unit tests; full suite 760 passed.

cli/src/native/mod.rs

@@ -1,6 +1,8 @@
 #[allow(dead_code)]
 pub mod actions;
 #[allow(dead_code)]
+pub mod adaptive;
+#[allow(dead_code)]
 pub mod auth;
 #[allow(dead_code)]
 pub mod browser;