refactor(http): centralize User-Agent string in mozart-core

Add mozart_core::http::user_agent() that returns a consistent
"Mozart/<version> (<os>; <arch>)" string. Replace all scattered
user-agent definitions across mozart-registry and mozart CLI commands.

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

2 files changed, 4 insertions, 4 deletions

diff --git a/crates/mozart/src/commands/diagnose.rs b/crates/mozart/src/commands/diagnose.rs
index da37137..dc1ea85 100644
--- a/crates/mozart/src/commands/diagnose.rs
+++ b/crates/mozart/src/commands/diagnose.rs
@@ -83,7 +83,7 @@ async fn check_http_connectivity(url: &str) -> CheckResult {
 
     let client = match reqwest::Client::builder()
         .timeout(std::time::Duration::from_secs(10))
-        .user_agent(concat!("mozart/", env!("CARGO_PKG_VERSION")))
+        .user_agent(mozart_core::http::user_agent())
         .build()
     {
         Ok(c) => c,
@@ -111,7 +111,7 @@ async fn check_github_api() -> CheckResult {
 
     let client = match reqwest::Client::builder()
         .timeout(std::time::Duration::from_secs(10))
-        .user_agent(concat!("mozart/", env!("CARGO_PKG_VERSION")))
+        .user_agent(mozart_core::http::user_agent())
         .build()
     {
         Ok(c) => c,
diff --git a/crates/mozart/src/commands/self_update.rs b/crates/mozart/src/commands/self_update.rs
index 9f6a7fe..ad9ae74 100644
--- a/crates/mozart/src/commands/self_update.rs
+++ b/crates/mozart/src/commands/self_update.rs
@@ -133,7 +133,7 @@ async fn fetch_releases(include_prerelease: bool) -> anyhow::Result<Vec<GitHubRe
 
     let client = reqwest::Client::builder()
         .timeout(std::time::Duration::from_secs(30))
-        .user_agent(concat!("mozart/", env!("CARGO_PKG_VERSION")))
+        .user_agent(mozart_core::http::user_agent())
         .build()
         .map_err(|e| anyhow::anyhow!("Could not build HTTP client: {e}"))?;
 
@@ -212,7 +212,7 @@ async fn download_asset(
 ) -> anyhow::Result<()> {
     let client = reqwest::Client::builder()
         .timeout(std::time::Duration::from_secs(300))
-        .user_agent(concat!("mozart/", env!("CARGO_PKG_VERSION")))
+        .user_agent(mozart_core::http::user_agent())
         .build()
         .map_err(|e| anyhow::anyhow!("Could not build HTTP client: {e}"))?;