chore: archive historical task programs

docs/archived/alpha-hardening/issues/12-c2-on-chain-idempotency.md

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+Status: ready-for-human
+
+# 12 — C2: On-chain settlement idempotency (deferred)
+
+## What to build
+
+Harden payout idempotency so Solana transaction retries never double-pay. Design accepted in ADR-0019 §1; **implementation deferred post-alpha**.
+
+**Code refs:**
+
+- `packages/tracker/meshnet_tracker/server.py` — `_settlement_loop` resend (~3331–3356), `_send_settlement` (~3358–3376)
+- `packages/contracts/meshnet_contracts/solana_adapter.py` — `send_payouts` (~186–213)
+
+Today: pending debited before broadcast with stable `settlement_id`; unconfirmed batches resent. Gap: on-chain confirmation vs ledger state if tx succeeds but confirm fails.
+
+## Acceptance criteria
+
+- [ ] `confirm_settlement` only after RPC finalized confirmation
+- [ ] Retry path reuses same `settlement_id` and detects already-confirmed signature
+- [ ] Property test: N retries → single on-chain transfer per wallet per settlement_id
+- [ ] Document recovery procedure for stuck unconfirmed batches
+
+## ADR links
+
+- [ADR-0019](../../docs/adr/0019-money-path-consistency-multi-tracker.md) §1
+
+## Blocked by
+
+Alpha release (ADR-0016 single settlement tracker)