bootstrap-rc: seed the release pair into rc, not just the promoted set

Eligibility used package_moves_to_channel, which excludes packages built
natively in the destination — right for ongoing edge -> rc advances (a native
build must not be raced under the same filename) but wrong for the bootstrap,
whose entire purpose is rc == stable. omarchy and omarchy-settings were
therefore left out, so a machine switched to the rc channel could not install
or update the release pair until the first RC was cut. The bootstrap now
requires only destination membership; nothing is built in rc yet, so there is
no native artifact to conflict with. The dev pair stays edge-only and
fast-ring replication is unchanged.

bin/advance-channel

@@ -208,6 +208,15 @@ package_eligible() {
     package_is_fast_ring "$pkgdir" && return 1
   fi
 
+  # The bootstrap seeds an empty rc from stable, so parity is the whole point:
+  # membership in the destination is enough. Nothing is built in rc yet, so
+  # there is no native artifact to race — and the release pair MUST come along
+  # or rc cannot serve omarchy/omarchy-settings until the first RC is cut.
+  if [[ "$BOOTSTRAP" == true ]]; then
+    package_in_channel "$pkgdir" "$TO"
+    return
+  fi
+
   package_moves_to_channel "$pkgdir" "$TO"
 }