fix(global): add ~/.composer fallback, XDG auto-detection, and no-arg handling

Rewrite composer_home() with Composer-compatible resolution: detect XDG
environment (any XDG_* var or /etc/xdg), prefer existing directories,
and fall back to ~/.composer for legacy systems. Consolidate duplicate
composer_home_dir() from global.rs into shared config_helpers. Accept
no subcommand gracefully with a helpful error instead of a parse error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/crates/mozart-autoload/src/autoload.rs b/crates/mozart-autoload/src/autoload.rs
index 8d59db5..97fb9b0 100644
--- a/crates/mozart-autoload/src/autoload.rs
+++ b/crates/mozart-autoload/src/autoload.rs
@@ -857,9 +857,10 @@ pub fn generate(config: &AutoloadConfig) -> anyhow::Result<GenerateResult> {
         );
         for (class, path_expr) in scanned {
             if let Some(existing) = data.classmap.get(&class)
-                && existing != &path_expr {
-                    ambiguous_found = true;
-                }
+                && existing != &path_expr
+            {
+                ambiguous_found = true;
+            }
             // Also generate the static expression
             // We store the dynamic expression in data.classmap; static_data.classmap
             // will be populated similarly. For now we insert into both.
@@ -884,9 +885,10 @@ pub fn generate(config: &AutoloadConfig) -> anyhow::Result<GenerateResult> {
         psr_violations = violations;
         for (class, path_expr) in opt_dyn {
             if let Some(existing) = data.classmap.get(&class)
-                && existing != &path_expr {
-                    ambiguous_found = true;
-                }
+                && existing != &path_expr
+            {
+                ambiguous_found = true;
+            }
             data.classmap.entry(class).or_insert(path_expr);
         }
         for (class, path_expr) in opt_static {