feat(config): add manual registry-rebuild command

functions/__fish_config_op_registry_rebuild.fish

@@ -0,0 +1,30 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+# SYNOPSIS
+#   __fish_config_op_registry_rebuild
+#
+# DESCRIPTION
+#   Regenerates conf.d/__fish_config_op_registry.fish from every
+#   # COMPONENT header in functions/*.fish, conf.d/*.fish, and
+#   config.fish, then re-sources it into the current session so the
+#   change takes effect immediately. Run manually after editing a
+#   # COMPONENT header; never run automatically at shell startup --
+#   parsing every header on every new shell would be wasted work on
+#   every session that isn't actively editing a header.
+#
+# EXIT STATUS
+#   0  Registry regenerated
+#   1  python3 is not available, or generation failed
+#
+# EXAMPLE
+#   __fish_config_op_registry_rebuild
+function __fish_config_op_registry_rebuild --description 'Regenerate the opinionated-component registry from # COMPONENT headers'
+    if not type -q python3
+        echo "__fish_config_op_registry_rebuild: python3 not found" >&2
+        return 1
+    end
+    python3 "$__fish_config_dir/docs/generate_component_registry.py"
+    or return 1
+    source "$__fish_config_dir/conf.d/__fish_config_op_registry.fish"
+end