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>

6 files changed, 26 insertions, 8 deletions

diff --git a/crates/mozart-core/src/http.rs b/crates/mozart-core/src/http.rs
new file mode 100644
index 0000000..ebd28f9
--- /dev/null
+++ b/crates/mozart-core/src/http.rs
@@ -0,0 +1,11 @@
+/// Returns the common User-Agent string for all HTTP requests.
+///
+/// Format: `Mozart/<version> (<os>; <arch>)`
+pub fn user_agent() -> String {
+    format!(
+        "Mozart/{} ({}; {})",
+        env!("CARGO_PKG_VERSION"),
+        std::env::consts::OS,
+        std::env::consts::ARCH,
+    )
+}
diff --git a/crates/mozart-core/src/lib.rs b/crates/mozart-core/src/lib.rs
index b02e5a3..aef7af3 100644
--- a/crates/mozart-core/src/lib.rs
+++ b/crates/mozart-core/src/lib.rs
@@ -1,5 +1,6 @@
 pub mod console;
 pub mod exit_code;
+pub mod http;
 pub mod package;
 pub mod platform;
 pub mod suggest;
diff --git a/crates/mozart-registry/src/downloader.rs b/crates/mozart-registry/src/downloader.rs
index 9a5ed24..8bd99c7 100644
--- a/crates/mozart-registry/src/downloader.rs
+++ b/crates/mozart-registry/src/downloader.rs
@@ -108,7 +108,10 @@ pub async fn download_dist(
         }
     }
 
-    let response = reqwest::get(url).await?;
+    let client = reqwest::Client::builder()
+        .user_agent(mozart_core::http::user_agent())
+        .build()?;
+    let response = client.get(url).send().await?;
 
     if !response.status().is_success() {
         anyhow::bail!(
diff --git a/crates/mozart-registry/src/packagist.rs b/crates/mozart-registry/src/packagist.rs
index e851955..ac290fb 100644
--- a/crates/mozart-registry/src/packagist.rs
+++ b/crates/mozart-registry/src/packagist.rs
@@ -215,7 +215,10 @@ pub async fn fetch_package_versions(
 
     // Cache miss — fetch from Packagist
     let url = format!("https://repo.packagist.org/p2/{package_name}.json");
-    let response = reqwest::get(&url).await?;
+    let client = reqwest::Client::builder()
+        .user_agent(mozart_core::http::user_agent())
+        .build()?;
+    let response = client.get(&url).send().await?;
 
     if !response.status().is_success() {
         anyhow::bail!(
@@ -285,7 +288,7 @@ pub async fn search_packages(
     package_type: Option<&str>,
 ) -> anyhow::Result<(Vec<SearchResult>, u64)> {
     let client = reqwest::Client::builder()
-        .user_agent("mozart/0.1.0")
+        .user_agent(mozart_core::http::user_agent())
         .build()?;
 
     let mut all_results: Vec<SearchResult> = Vec::new();
@@ -396,7 +399,7 @@ pub async fn fetch_security_advisories(
     package_names: &[&str],
 ) -> anyhow::Result<BTreeMap<String, Vec<SecurityAdvisory>>> {
     let client = reqwest::Client::builder()
-        .user_agent("mozart/0.1.0")
+        .user_agent(mozart_core::http::user_agent())
         .build()?;
 
     let mut all_advisories: BTreeMap<String, Vec<SecurityAdvisory>> = BTreeMap::new();
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}"))?;