fix: use quoted "m3ta-home" namespace (consistent with repo name)

modules/paths.nix

@@ -2,9 +2,9 @@
 #
 # Relative paths with ../.. break in the Nix store during pure evaluation.
 # This module exposes the flake source root so other modules can reference
-# assets via config.m3taHome.paths.srcRoot.
+# assets via config."m3ta-home".paths.srcRoot.
 {lib, ...}: {
-  options.m3taHome.paths = {
+  options."m3ta-home".paths = {
     srcRoot = lib.mkOption {
       type = lib.types.path;
       description = "Root path of the m3ta-home flake source (set by flake.nix).";