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/01-c1-gossip-auth.md

@@ -0,0 +1,41 @@
+Status: ready-for-agent
+
+# 01 — C1: Authenticate hive gossip endpoints
+
+## What to build
+
+Add authenticated peer identity to all tracker gossip mutation endpoints. Today any caller can push billing, account, and stats events without verification.
+
+**Code refs:**
+
+- `packages/tracker/meshnet_tracker/server.py` — `_handle_billing_gossip` (~2414–2427)
+- `packages/tracker/meshnet_tracker/server.py` — `_handle_accounts_gossip` (~2610–2623)
+- `packages/tracker/meshnet_tracker/server.py` — `_handle_stats_gossip` (~2355–2364)
+- `packages/tracker/meshnet_tracker/billing.py` — `apply_events` (~301–311)
+- `packages/tracker/meshnet_tracker/accounts.py` — `apply_events` (~220–226)
+
+Implement per ADR-0017 §3: shared hive HMAC (body + timestamp) or mutual TLS between configured tracker peers. Reject unauthenticated gossip with 401.
+
+**Note:** `/v1/gossip` (node throughput fan-out, `server.py` ~1331) is **not** in scope for this issue — see ADR-0017 §3 out-of-scope note.
+
+## Test-first
+
+1. Red: unauthenticated POST to `/v1/billing/gossip` applies a credit event today — test must fail after fix.
+2. Red: authenticated peer with valid HMAC applies events; invalid/missing auth returns 401 and `applied: 0`.
+3. Green: implement verifier + config (`--hive-secret` or peer cert paths).
+
+## Acceptance criteria
+
+- [ ] `/v1/billing/gossip`, `/v1/accounts/gossip`, `/v1/stats/gossip` reject requests without valid hive auth
+- [ ] Authenticated peers replicate events as today (id-dedup preserved)
+- [ ] Config documented for multi-tracker dev setups
+- [ ] Tests cover reject + accept paths without live network
+
+## ADR links
+
+- [ADR-0017](../../docs/adr/0017-tracker-authentication-and-authorization.md)
+- [ADR-0016](../../docs/adr/0016-alpha-scope-and-known-limitations.md)
+
+## Blocked by
+
+None — implement alongside or immediately before `02-a2-unified-auth-boundary.md`.