Split view, personal modes, budget warnings, server move script

- Up to three chats side by side (#/s/a+b+c), "Open beside" in the sidebar menu
- File manager tabs of a chat stored per user on the server (/sessions/{id}/tabs)
- Personal modes for every user (Settings → My modes, /account/modes)
- Budget meters (total, provider, images, opencode Go windows) with push warnings
  for admins at the warning share and 100 %, shown in the status overlay
- scripts/move-server.sh: move to another Docker host with bind mounts (Unraid);
  scripts/smoke-test.sh

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/prompts.rs

@@ -147,8 +147,40 @@ pub fn agents(app: &App, root: &Path, cwd: &Path) -> Vec<Agent> {
     map.into_values().collect()
 }
 
-pub fn find_agent(app: &App, root: &Path, cwd: &Path, name: &str) -> Agent {
-    agents(app, root, cwd)
+/// Personal modes a user created for themselves (user setting "modes").
+pub fn personal_modes(app: &App, user_id: &str) -> BTreeMap<String, crate::config::AgentConfig> {
+    app.store.user_setting(user_id, "modes").unwrap_or_default()
+}
+
+/// All agents plus the user's personal modes. Personal modes never replace built-in,
+/// admin or project ones of the same name.
+pub fn agents_for(app: &App, root: &Path, cwd: &Path, user_id: Option<&str>) -> Vec<Agent> {
+    let mut list = agents(app, root, cwd);
+    let Some(uid) = user_id else { return list };
+    for (name, a) in personal_modes(app, uid) {
+        if list.iter().any(|x| x.name == name) {
+            continue;
+        }
+        list.push(Agent {
+            name,
+            description: a.description.unwrap_or_default(),
+            mode: "primary".into(),
+            prompt: a.prompt.unwrap_or_default(),
+            tools: a.tools,
+            read_only: a.read_only.unwrap_or(false),
+            style: a.style.filter(|s| s == "chat").unwrap_or_else(|| "coding".into()),
+            model: a.model.filter(|m| !m.is_empty()),
+            source: "personal".into(),
+            max_parallel: None,
+            refine: a.refine,
+            path: None,
+        });
+    }
+    list
+}
+
+pub fn find_agent_for(app: &App, root: &Path, cwd: &Path, name: &str, user_id: Option<&str>) -> Agent {
+    agents_for(app, root, cwd, user_id)
         .into_iter()
         .find(|a| a.name == name)
         .unwrap_or_else(|| builtin_agents(true).remove(0))