feat(core): port Factory::createConfig() as factory::create_config()

Adds crates/mozart-core/src/factory.rs with get_cache_dir(),
get_data_dir(), and create_config() — a Rust port of
Composer\Factory::createConfig() (auth loading and htaccess creation
are out of scope for now).

Also fixes a correctness bug on Linux: the previous Config::default()
resolved cache-dir to $XDG_CONFIG_HOME/composer/cache via the
{$home}/cache placeholder, whereas Composer uses the XDG cache base
($XDG_CACHE_HOME or ~/.cache), giving ~/.cache/composer.

Callers updated:
- Composer::load() uses create_config() as the global baseline before
  merging project-level config.
- config command execute_read() builds the global baseline with
  create_config() and overlays local config on top when not --global,
  matching Composer's actual layering order.

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

1 files changed, 7 insertions, 7 deletions

diff --git a/crates/mozart/src/commands/config.rs b/crates/mozart/src/commands/config.rs
index 40336f3..274dcde 100644
--- a/crates/mozart/src/commands/config.rs
+++ b/crates/mozart/src/commands/config.rs
@@ -60,7 +60,8 @@ pub struct ConfigArgs {
     pub source: bool,
 }
 
-use mozart_core::config::{Config, resolve_references};
+use mozart_core::config::resolve_references;
+use mozart_core::factory::create_config;
 
 /// Classification of config key value types for validation and normalization.
 #[derive(Debug)]
@@ -754,13 +755,11 @@ fn execute_read(
     console: &mozart_core::console::Console,
 ) -> anyhow::Result<()> {
     // Build the effective config for config-section keys.
-    let mut config = Config::default();
+    // Global baseline (defaults + platform dirs + $COMPOSER_HOME/config.json),
+    // then overlay project config on top when not in --global mode.
+    let mut config = create_config()?;
 
-    if args.global {
-        let global_config_path = composer_home().join("config.json");
-        let overrides = load_config_section(&global_config_path)?;
-        config.merge(&overrides)?;
-    } else {
+    if !args.global {
         let wd = cli.working_dir()?;
         let composer_json = wd.join("composer.json");
         let overrides = load_config_section(&composer_json)?;
@@ -857,6 +856,7 @@ fn execute_read(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use mozart_core::config::Config;
 
     #[test]
     fn test_defaults_contain_expected_keys() {