Add alpha-hardening ADRs and issue plan from pre-release audit.

Lock alpha scope, tracker auth, TOPLOC fraud verification, and deferred multi-tracker money-path work; supersede legacy fraud issues with ADR-0018.

Co-authored-by: Cursor <cursoragent@cursor.com>

.scratch/alpha-hardening/issues/11-c6-wallet-binding-proof.md

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+Status: ready-for-agent
+
+# 11 — C6: Wallet binding ownership proof + binding overwrite safety
+
+## What to build
+
+`POST /v1/wallet/register` binds a client Solana wallet to an API key for deposit attribution. Today any Bearer key can bind any wallet string without proving ownership. Prevent hijack and accidental overwrite.
+
+**Code refs:**
+
+- `packages/tracker/meshnet_tracker/server.py` — `_handle_wallet_register` (~2625–2648)
+- `packages/tracker/meshnet_tracker/billing.py` — `bind_wallet` (~153+), `_wallet_bindings` / direct overwrite on apply (~351)
+
+Require signed message from wallet pubkey (ed25519 via `cryptography` / solders). Reject rebinding without admin or signed release. Use explicit overwrite policy — today `~351` overwrites binding directly; gossip apply must reject conflicting binds instead of silently clobbering.
+
+## Test-first
+
+1. Red: bind wallet A with only API key, no signature — must fail after fix.
+2. Red: wallet already bound to key1; key2 cannot steal without proof.
+3. Green: valid signature binds; deposit watcher credits correct API key.
+
+## Acceptance criteria
+
+- [ ] Wallet binding requires cryptographic proof of pubkey ownership
+- [ ] One wallet → one API key (or documented admin override)
+- [ ] Gossip `bind` events cannot overwrite existing binding via direct overwrite at `~351`
+- [ ] Tests with deterministic keypairs (local adapter)
+
+## ADR links
+
+- [ADR-0017](../../docs/adr/0017-tracker-authentication-and-authorization.md) §5
+- [ADR-0015](../../docs/adr/0015-usdt-custodial-settlement.md)
+
+## Blocked by
+
+- `02-a2-unified-auth-boundary.md`
+- `03-c5-starting-credit-zero.md`