feat: USDT reward system — billing ledger, devnet treasury, settlement loop, forfeiture PoW, tracker dashboard (US-030…US-035, ADR-0015)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/validator/README.md

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+# meshnet-validator
+
+Optimistic fraud detection (ADR-0003, penalty amended by ADR-0015): the
+validator re-runs a random ~5% sample of completed inference requests against
+a trusted reference node and, on divergence, submits a slash proof and
+forfeits the node's pending balance.
+
+## Why the penalty deters cheating
+
+There is no upfront stake. Settlement is periodic (US-033), so a node always
+has an unpaid **pending balance** — that balance *is* the collateral.
+
+At a sampling rate `p`, a cheater is caught on average once every `1/p`
+fraudulent jobs, so cheating is unprofitable when:
+
+```
+penalty > per_job_gain / p        # p = 0.05  →  penalty > 20 × per_job_gain
+```
+
+With the production settlement period of 24h, the pending balance at any
+moment approximates a full day's earnings — hundreds to thousands of jobs —
+which is far above the 20× bar. Each catch also records a strike; three
+strikes ban the wallet (registration rejected, excluded from routes, unpaid
+pending never settled), and the probationary period (first N jobs unpaid)
+makes re-entry with a fresh wallet costly.
+
+Two operational notes:
+
+- Shortening the settlement period shrinks the collateral. Period changes
+  must weigh chain overhead against deterrence.
+- A cheater immediately after a payout has little to forfeit — the
+  strike/ban ladder covers that window.
+
+## Usage
+
+```python
+ValidatorProcess(
+    contracts=contracts,          # registry/validation boundary
+    billing=ledger,               # BillingLedger — enables forfeiture
+    reference_node_url="http://...",
+    sample_rate=0.05,
+)
+```
+
+Remote validators can instead call the tracker's privileged
+`POST /v1/billing/forfeit` endpoint (non-empty Authorization header).