fix: vision(#623): per-project subdomain fallback path (contingency) (#713)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tools/edge-control/register.sh

@@ -39,6 +39,11 @@ EOF
   exit 1
 }
 
+# TODO(#713): Subdomain fallback — if subpath routing (#704/#708) fails, this
+# function would need to register additional routes for forge.<project>,
+# ci.<project>, chat.<project> subdomains (or accept a --subdomain parameter).
+# See docs/edge-routing-fallback.md for the full pivot plan.
+
 # Register a new tunnel
 # Usage: do_register <project> <pubkey>
 do_register() {