release(v1.7.26-alpha): mirror list + origin-relative download URLs

Adds a multi-mirror manifest fetch. `check_for_updates` walks a
configurable list (data_dir/update-mirrors.json) in priority order
and falls through to the next mirror on any HTTP / parse / timeout
failure. Two defaults bake in: Server 1 (git.tx1138.com) and Server 2
(23.182.128.160:3000).

Critical fix: after parsing a manifest, rewrite every component's
`download_url` so its origin matches the manifest URL we fetched.
Before this, the manifest hard-coded absolute URLs pointing at one
specific server — so even when a node fetched the manifest from a
faster mirror, the actual 200MB download went back to the slow
original. Now the faster mirror wins end-to-end.

New RPCs: update.list-mirrors, update.add-mirror, update.remove-mirror,
update.set-primary-mirror. New UI section on the System Update page
for operator management. 5 new unit tests for origin parsing and
manifest rewriting (21/21 green).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

core/archipelago/src/api/rpc/dispatcher.rs

@@ -431,6 +431,19 @@ impl RpcHandler {
             "update.dismiss" => self.handle_update_dismiss().await,
             "update.download" => self.handle_update_download().await,
             "update.cancel-download" => self.handle_update_cancel_download().await,
+            "update.list-mirrors" => self.handle_update_list_mirrors().await,
+            "update.add-mirror" => {
+                let p = params.unwrap_or(serde_json::json!({}));
+                self.handle_update_add_mirror(&p).await
+            }
+            "update.remove-mirror" => {
+                let p = params.unwrap_or(serde_json::json!({}));
+                self.handle_update_remove_mirror(&p).await
+            }
+            "update.set-primary-mirror" => {
+                let p = params.unwrap_or(serde_json::json!({}));
+                self.handle_update_set_primary_mirror(&p).await
+            }
             "update.apply" => self.handle_update_apply().await,
             "update.git-apply" => self.handle_update_git_apply().await,
             "update.rollback" => self.handle_update_rollback().await,

core/archipelago/src/api/rpc/update.rs

@@ -241,6 +241,75 @@ impl RpcHandler {
         Ok(serde_json::json!({ "rolled_back": true, "restart_required": true }))
     }
 
+    /// List configured update mirrors in priority order.
+    pub(super) async fn handle_update_list_mirrors(&self) -> Result<serde_json::Value> {
+        let list = update::load_mirrors(&self.config.data_dir).await?;
+        Ok(serde_json::json!({ "mirrors": list }))
+    }
+
+    /// Add a mirror to the end of the list. Params: `{ url, label? }`.
+    /// Duplicates (same URL) are replaced rather than added twice.
+    pub(super) async fn handle_update_add_mirror(
+        &self,
+        params: &serde_json::Value,
+    ) -> Result<serde_json::Value> {
+        let url = params
+            .get("url")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow::anyhow!("missing url"))?
+            .trim()
+            .to_string();
+        if !url.starts_with("http://") && !url.starts_with("https://") {
+            anyhow::bail!("url must start with http:// or https://");
+        }
+        let label = params
+            .get("label")
+            .and_then(|v| v.as_str())
+            .unwrap_or("")
+            .trim()
+            .to_string();
+        let mut list = update::load_mirrors(&self.config.data_dir).await?;
+        list.retain(|m| m.url != url);
+        list.push(update::UpdateMirror { url, label });
+        update::save_mirrors(&self.config.data_dir, &list).await?;
+        Ok(serde_json::json!({ "mirrors": list }))
+    }
+
+    /// Remove a mirror by URL. Params: `{ url }`.
+    pub(super) async fn handle_update_remove_mirror(
+        &self,
+        params: &serde_json::Value,
+    ) -> Result<serde_json::Value> {
+        let url = params
+            .get("url")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow::anyhow!("missing url"))?;
+        let mut list = update::load_mirrors(&self.config.data_dir).await?;
+        list.retain(|m| m.url != url);
+        update::save_mirrors(&self.config.data_dir, &list).await?;
+        Ok(serde_json::json!({ "mirrors": list }))
+    }
+
+    /// Move a mirror to the top of the list so it's tried first.
+    /// Params: `{ url }`.
+    pub(super) async fn handle_update_set_primary_mirror(
+        &self,
+        params: &serde_json::Value,
+    ) -> Result<serde_json::Value> {
+        let url = params
+            .get("url")
+            .and_then(|v| v.as_str())
+            .ok_or_else(|| anyhow::anyhow!("missing url"))?;
+        let mut list = update::load_mirrors(&self.config.data_dir).await?;
+        let Some(idx) = list.iter().position(|m| m.url == url) else {
+            anyhow::bail!("mirror not in list");
+        };
+        let entry = list.remove(idx);
+        list.insert(0, entry);
+        update::save_mirrors(&self.config.data_dir, &list).await?;
+        Ok(serde_json::json!({ "mirrors": list }))
+    }
+
     /// Get the current update schedule.
     pub(super) async fn handle_update_get_schedule(&self) -> Result<serde_json::Value> {
         let schedule = update::get_schedule(&self.config.data_dir).await?;