feat(config): add component registry lookup helper

functions/__fish_config_op_registry_lookup.fish

@@ -0,0 +1,38 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+# SYNOPSIS
+#   __fish_config_op_registry_lookup <identity> <site>
+#
+# DESCRIPTION
+#   Looks up the "<identity>:<site>" key in the generated component
+#   registry ($__fish_config_op_registry_keys /
+#   $__fish_config_op_registry_values, sourced from
+#   conf.d/__fish_config_op_registry.fish at shell startup) and prints its
+#   tags, one per line. <site> is empty string for the default/unnamed
+#   site.
+#
+# ARGUMENTS
+#   identity  Function name (status current-function) or file basename
+#             with any trailing .fish stripped (status basename)
+#   site      Site slug, or empty string for the default site
+#
+# EXIT STATUS
+#   0  Found: tags printed to stdout
+#   1  Not found: nothing printed
+#
+# RETURNS
+#   Matching tags, one per line, printed to stdout
+#
+# EXAMPLE
+#   set -l tags (__fish_config_op_registry_lookup rm "")
+#   or return 0   # unclassified: caller treats this as always-on
+function __fish_config_op_registry_lookup --description 'Look up the COMPONENT tags for an identity:site pair'
+    set -l key "$argv[1]:$argv[2]"
+    set -l idx (contains -i -- $key $__fish_config_op_registry_keys)
+    if test -z "$idx"
+        return 1
+    end
+    string split ' ' -- $__fish_config_op_registry_values[$idx]
+    return 0
+end