Merge master into refactor-hotpath-next

Bring master's runtime peer-list refresh, opt-in mDNS LAN discovery, and
the receive-path reject-reason / reloadable-config refactor into the XX
handshake integration branch. The peer-restart-epoch detection and
stale-FSP-session teardown authored against Noise IK are re-authored onto
the Noise XX rekey path: complete_rekey_msg2 now also surfaces the remote
startup epoch, and the stale session is cleared once the XX rekey
completes (after msg3 is sent). Connect-budget and path-refresh work is
threaded through the XX anonymous-discovery branch.

src/control/snapshots/show_routing.json

@@ -11,6 +11,7 @@
       "req_backoff_suppressed": 0,
       "req_bloom_miss": 0,
       "req_decode_error": 0,
+      "req_dedup_cache_full": 0,
       "req_deduplicated": 0,
       "req_duplicate": 0,
       "req_fallback_forwarded": 0,