fix(upgrade): set Accept header for GitHub asset download

GitHub release asset URLs are API endpoints
(api.github.com/repos/.../assets/XXX) that return JSON metadata by default,
not the binary. Without `Accept: application/octet-stream`, the downloaded
"archive" was actually JSON, causing tar extraction to fail with
"Could not find the required path in the archive".

self_update::ReleaseUpdate::update() sets this header internally; since we
bypass it and use Download directly, we must set it ourselves. Also adds a
User-Agent header (GitHub API requires one).

Author: wuguofeng

Cargo.lock

@@ -42,6 +42,12 @@ tokio = { version = "1", features = ["macros", "signal", "time", "sync"] }
 # blocks cross-major upgrades (0.x → 1.0). rustls backend (no OpenSSL).
 self_update = { version = "0.42", default-features = false, features = ["archive-tar", "compression-flate2", "rustls"] }
 
+# HTTP header types for the upgrade download. GitHub asset API URLs need
+# `Accept: application/octet-stream` to return the binary (not JSON metadata);
+# we construct that header via reqwest::header (reqwest is already pulled in
+# by self_update, so this adds no new code to the binary).
+reqwest = { version = "0.12", default-features = false, features = ["rustls-tls"] }
+
 # Atomic self-replacement of the running binary. Re-exported by self_update as
 # `self_update::self_replace`, but depended on directly here for clarity (we
 # call it from our own download+replace logic, not from self_update's).

crates/core/Cargo.toml

@@ -201,7 +201,28 @@ impl UpgradeEngine {
         let archive_path = tmp_dir.path().join(&asset.name);
         let mut archive_file =
             std::fs::File::create(&archive_path).map_err(|e| format!("create archive file: {e}"))?;
-        self_update::Download::from_url(&asset.download_url)
+
+        // GitHub release asset URLs are API endpoints (api.github.com/.../assets/XXX)
+        // that return JSON metadata unless `Accept: application/octet-stream` is sent.
+        // Without this header, the downloaded "archive" is actually JSON → tar extraction
+        // fails with "Could not find the required path in the archive". This mirrors what
+        // self_update::ReleaseUpdate::update() does internally (api_headers + Accept).
+        let mut download = self_update::Download::from_url(&asset.download_url);
+        let mut headers = reqwest::header::HeaderMap::new();
+        headers.insert(
+            reqwest::header::ACCEPT,
+            "application/octet-stream"
+                .parse()
+                .map_err(|e| format!("invalid accept header: {e}"))?,
+        );
+        headers.insert(
+            reqwest::header::USER_AGENT,
+            concat!("tailr-upgrade/", env!("CARGO_PKG_VERSION"))
+                .parse()
+                .map_err(|e| format!("invalid user-agent header: {e}"))?,
+        );
+        download.set_headers(headers);
+        download
             .download_to(&mut archive_file)
             .map_err(|e| format!("download failed: {e}"))?;