feat(alpha): complete hardening backlog

Complete the alpha-hardening Ralph task set, including tracker billing/accounting guards, validator fraud-audit primitives, wallet binding proof support, documentation runbooks, and updated tests.

Verification: .venv/bin/python -m compileall -q packages tests; .venv/bin/python -m pytest -q --tb=short (313 passed, 3 skipped, 1 failed: tests/test_mining_cli.py::test_legacy_start_without_port_uses_next_available_port because meshnet-node pid 1263451 is already listening on port 7000).

.scratch/alpha-hardening/issues/07-fraud-commitment-bisection-blame.md

@@ -1,4 +1,4 @@
-Status: ready-for-agent
+Status: done
 
 # 07 — FRAUD: On-demand commitment + hop bisection blame
 
@@ -20,11 +20,11 @@ On audit selection, require nodes to supply TOPLOC-style fingerprints of **outpu
 
 ## Acceptance criteria
 
-- [ ] Audit requests carry tracker RNG/VRF flag indistinguishable from normal traffic (research §6)
-- [ ] Nodes retain recent boundary activations for on-demand commit window (configurable TTL)
-- [ ] Validator/tracker compares fingerprints at each hop cut-point; first mismatch = culprit
-- [ ] `_final_text_node` removed or limited to text-only fallback
-- [ ] Integration test: multi-hop pipeline, fault injected at known hop
+- [x] Audit requests carry tracker RNG/VRF flag indistinguishable from normal traffic (research §6) — the existing post-hoc `sample_rate` RNG gate in `ValidatorProcess.validate_once` already decides audit selection after the original proxied request completed, so the request the client/nodes saw is unaffected either way; locked in by `test_hop_commitments_are_not_requested_unless_the_event_is_audit_selected`
+- [x] Nodes retain recent boundary activations for on-demand commit window (configurable TTL) — `ToplocAuditConfig.commitment_ttl_seconds`; expired commitments fall back to the text-only path (`test_expired_commitment_window_falls_back_to_text_only_audit`)
+- [x] Validator/tracker compares fingerprints at each hop cut-point; first mismatch = culprit — `_hop_commitments_from_event` + `_first_divergent_hop` in `packages/validator/meshnet_validator/__init__.py`
+- [x] `_final_text_node` removed or limited to text-only fallback — only called from the plain-text divergence branch of `_validate_event` now
+- [x] Integration test: multi-hop pipeline, fault injected at known hop — `tests/test_hop_bisection.py`
 
 ## ADR links