feat(core): add Composer struct mirroring requireComposer/tryComposer

Introduce mozart_core::composer::Composer with require()/try_load()
constructors and a config() accessor, modelled on PHP Composer's
BaseCommand::requireComposer / tryComposer. ComposerConfig and
composer_home move into mozart-core so Composer::load can resolve
placeholders consistently.

Migrate dump-autoload, archive, exec and run-script away from ad-hoc
composer.json reads. exec and run-script now fail when composer.json
is missing instead of silently falling back to "vendor/bin",
matching the upstream requireComposer contract.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 1 insertions, 58 deletions

diff --git a/crates/mozart/src/commands/config_helpers.rs b/crates/mozart/src/commands/config_helpers.rs
index 422db4d..2f856a7 100644
--- a/crates/mozart/src/commands/config_helpers.rs
+++ b/crates/mozart/src/commands/config_helpers.rs
@@ -1,64 +1,7 @@
 use anyhow::anyhow;
 use std::path::{Path, PathBuf};
 
-/// Return the Composer home directory, respecting `COMPOSER_HOME` and
-/// falling back to the platform default using Composer-compatible logic.
-///
-/// On Unix:
-/// - If XDG is in use (any `XDG_*` env var exists, or `/etc/xdg` exists),
-///   prefer `$XDG_CONFIG_HOME/composer` (or `$HOME/.config/composer`).
-/// - Always include `$HOME/.composer` as a fallback candidate.
-/// - Return the first candidate directory that exists on disk;
-///   if none exist, return the first candidate.
-pub(crate) fn composer_home() -> PathBuf {
-    if let Ok(val) = std::env::var("COMPOSER_HOME")
-        && !val.is_empty()
-    {
-        return PathBuf::from(val);
-    }
-
-    #[cfg(target_os = "windows")]
-    {
-        if let Ok(appdata) = std::env::var("APPDATA")
-            && !appdata.is_empty()
-        {
-            return PathBuf::from(appdata).join("Composer");
-        }
-        return PathBuf::from("C:/ProgramData/ComposerSetup/bin");
-    }
-
-    #[cfg(not(target_os = "windows"))]
-    {
-        let home_dir = std::env::var("HOME")
-            .map(PathBuf::from)
-            .unwrap_or_else(|_| PathBuf::from("/tmp"));
-
-        let mut candidates: Vec<PathBuf> = Vec::new();
-
-        if use_xdg() {
-            let xdg_config = std::env::var("XDG_CONFIG_HOME")
-                .map(PathBuf::from)
-                .unwrap_or_else(|_| home_dir.join(".config"));
-            candidates.push(xdg_config.join("composer"));
-        }
-
-        candidates.push(home_dir.join(".composer"));
-
-        // Return first candidate that exists; otherwise return the first
-        candidates
-            .iter()
-            .find(|p| p.is_dir())
-            .cloned()
-            .unwrap_or_else(|| candidates.into_iter().next().unwrap())
-    }
-}
-
-/// Check whether XDG base directories are in use:
-/// any env var starting with `XDG_` exists, OR `/etc/xdg` directory exists.
-fn use_xdg() -> bool {
-    std::env::vars().any(|(k, _)| k.starts_with("XDG_"))
-        || std::path::Path::new("/etc/xdg").is_dir()
-}
+pub(crate) use mozart_core::composer::composer_home;
 
 /// Build the working directory path, preferring `--working-dir` over `cwd`.
 pub(crate) fn working_dir(cli: &super::Cli) -> anyhow::Result<PathBuf> {