Add bin/repo push and stop sync from deleting production

Heavy packages build faster on a local machine, but there was no way to get
the artifacts to the server: bin/upload-prebuilt publishes to the rclone
remote from whatever tree it runs in, so the local -> host hop was manual.

bin/repo push rsyncs build-output artifacts to the host, verifies checksums,
and runs upload-prebuilt over ssh. Signing stays on the host, which is the
only machine with the key and the only one holding a complete repository.

Publishing from a local checkout was worse than merely unsupported. sync ran
rclone sync --delete-after against a tree that pkgs.omarchy.org/ gitignores,
so on any machine that had not run a full release it would have deleted the
production repository -- guarded only by a y/N prompt that --skip-prod-check
turns off. Package uploads are now additive, deletion moves behind --prune,
and sync refuses to publish a database built from a tree holding fewer
packages than the remote already lists.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

bin/repo

@@ -58,6 +58,7 @@ show_usage() {
   echo "  list        List source package metadata (use --repo for published repo)"
   echo "  remove      Remove a specific package"
   echo "  sync        Sync repository to remote"
+  echo "  push        Upload local builds to the build host and publish them there"
   echo ""
   echo "Typical workflows:"
   echo "  $0 release                  # Complete release workflow"
@@ -125,6 +126,10 @@ sync)
   "$SCRIPT_DIR/sync-repo" "$@" 2>&1 | tee "$LOG_FILE"
   exit ${PIPESTATUS[0]}
   ;;
+push)
+  "$SCRIPT_DIR/push-build" "$@" 2>&1 | tee "$LOG_FILE"
+  exit ${PIPESTATUS[0]}
+  ;;
 -h | --help | help)
   show_usage
   ;;