feat(update): implement update command with resolver-based dependency updates

Add full update command supporting --lock (content-hash refresh only),
--dry-run, --no-install, --no-dev, --prefer-stable, --prefer-lowest,
and partial updates (named packages). Extract install_from_lock() from
install.rs for shared use. Add Stability::parse() to package.rs.

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

1 files changed, 16 insertions, 0 deletions

diff --git a/crates/mozart/src/package.rs b/crates/mozart/src/package.rs
index e0e8c6c..e439ac5 100644
--- a/crates/mozart/src/package.rs
+++ b/crates/mozart/src/package.rs
@@ -17,6 +17,22 @@ pub enum Stability {
     Dev = 20,
 }
 
+impl Stability {
+    /// Parse a stability string (case-insensitive) into a `Stability` value.
+    ///
+    /// Recognizes: "stable", "RC", "beta", "alpha", "dev".
+    /// Defaults to `Stability::Stable` for unrecognized values.
+    pub fn parse(s: &str) -> Self {
+        match s.to_lowercase().as_str() {
+            "dev" => Stability::Dev,
+            "alpha" => Stability::Alpha,
+            "beta" => Stability::Beta,
+            "rc" => Stability::RC,
+            _ => Stability::Stable,
+        }
+    }
+}
+
 /// A versioned relationship between two packages.
 /// Corresponds to `Composer\Package\Link`.
 #[derive(Debug, Clone)]