fix(repository): align with Composer's RepositoryCommand pipeline

Introduce JsonConfigSource in mozart-core mirroring Composer's
JsonConfigSource fallback logic (add/insert/set-url/remove repository),
and BaseConfigContext mirroring BaseConfigCommand's initialize().

Key behaviour fixes:
- list: synthesise [packagist.org] <disabled> only when no composer-type
  repo with a packagist.org host is present (was: always show enabled default)
- disable: idempotent via add_repository(false) matching Composer's branch;
  now requires a name (no silent default to packagist.org)
- enable: calls remove_repository only, no extra empty-array cleanup
- set-url: preserves assoc-keyed format instead of converting to list
- get-url: assoc fast-path + unquoted error message matching Composer
- add: use regex pre-check (starts_with '{') instead of trial-parse
- error messages reworded to match Composer verbatim (mozart brand kept)

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

1 files changed, 35 insertions, 0 deletions

diff --git a/crates/mozart/src/commands/base_config.rs b/crates/mozart/src/commands/base_config.rs
new file mode 100644
index 0000000..be663d5
--- /dev/null
+++ b/crates/mozart/src/commands/base_config.rs
@@ -0,0 +1,35 @@
+use std::path::PathBuf;
+
+use mozart_core::config_source::JsonConfigSource;
+
+use super::config_helpers::composer_home;
+
+/// Mirrors Composer's `BaseConfigCommand`: resolves the target config file path
+/// and enforces the `--file` ↔ `--global` mutual exclusivity.
+pub(crate) struct BaseConfigContext {
+    pub config_source: JsonConfigSource,
+}
+
+impl BaseConfigContext {
+    pub fn initialize(
+        global: bool,
+        file: Option<&str>,
+        cli: &super::Cli,
+    ) -> anyhow::Result<Self> {
+        if global && file.is_some() {
+            anyhow::bail!("--file and --global can not be combined");
+        }
+
+        let path: PathBuf = if global {
+            composer_home().join("config.json")
+        } else if let Some(f) = file {
+            PathBuf::from(f)
+        } else {
+            cli.working_dir()?.join("composer.json")
+        };
+
+        Ok(Self {
+            config_source: JsonConfigSource::new(path, false),
+        })
+    }
+}