nostr: make /rvrelay a true pin -- never merge discovered relays

A pool started with /rvrelay=ONE still spawned an accept thread for every
Nostr-discovered relay (BtfAllRelays always merged g_discoveredRelays), and
each thread optimistically overwrote the advertised meeting node before
registering -- so a discovered Tailscale-only relay (a mesh host)
flapped the published .btf descriptor and public miners could not connect.

fBtfRelayPinned (set only when /rvrelay parses) makes BtfAllRelays return
exactly the pinned list. Also validate the /rvrelay value at parse time:
with the pin in place no discovered relay can mask a typo.

(cherry picked from commit 0a4d2b02fa5382c5e788b5f0e2f8a844695dec47)

1 files changed, 14 insertions, 2 deletions

diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 0b4e091..d0969b5 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -261,8 +261,20 @@ static void ParseStartupArguments(int argc, char* argv[])
     string rvRelay = argval2(argc, argv, "/rvrelay", "-rvrelay");
     if (!rvRelay.empty())
     {
-        vBtfMeetingRelays.clear();
-        vBtfMeetingRelays.push_back(rvRelay);
+        if (!LooksLikeRelay(rvRelay))
+        {
+            // A malformed pin must not replace the seed list: with the pin
+            // set, no discovered relay can ever mask the typo, and the pool
+            // would publish a garbage (or no) meeting node forever.
+            fprintf(stderr, "Ignoring /rvrelay=%s: expected host:port\n",
+                    rvRelay.c_str());
+        }
+        else
+        {
+            vBtfMeetingRelays.clear();
+            vBtfMeetingRelays.push_back(rvRelay);
+            fBtfRelayPinned = true;
+        }
     }
 
     string announceRelay = argval2(argc, argv, "/announcerelay", "-announcerelay");