feat: run shell commands asynchronously from command mode

docs/configuration.md

@@ -119,7 +119,7 @@ config.bind "leader s", config.core.diff.orientation.toggle
 
 Use the two setters independently; a combined `config.bar = { ... }` assignment is not supported.
 
-Defaults put `left: [:tabs]` and `right: [:battery]` in the top bar; the bottom has `left: [:mode, :pending, :buffer, :diagnostics, :path, :selections, :count]` and `right: [:language, :lsp, :position]`; other groups are empty. Set the bars independently, as in this swapped layout with status information above and tabs plus live battery charge below:
+Defaults put `left: [:tabs]` and `right: [:battery, :shell]` in the top bar; the bottom has `left: [:mode, :pending, :buffer, :diagnostics, :path, :selections, :count]` and `right: [:language, :lsp, :position]`; other groups are empty. Set the bars independently, as in this swapped layout with status information above and tabs plus live battery charge below:
 
 ```ruby
 Vamp.configure do |config|
@@ -130,7 +130,7 @@ Vamp.configure do |config|
     position: { padding: 1, leading_margin: 1, trailing_margin: 0, leading_edge: "░▓", trailing_edge: "" }
   }
   config.bar.bottom = {
-    left: [:tabs], center: [], right: [:battery],
+    left: [:tabs], center: [], right: [:battery, :shell],
     tabs: {
       title: "{index} {view}{name}{modified}", padding: 1,
       leading_edge: "░▓", trailing_edge: "▓░", first_leading_edge: ""
@@ -140,7 +140,7 @@ Vamp.configure do |config|
 end
 ```
 
-Builtins are `:tabs`, `:battery`, `:mode`, `:path`, `:position`, `:language`, `:lsp`, `:diagnostics`, `:selections`, `:count`, `:pending`, and `:buffer`, in either bar. They provide tab titles, battery charge, mode, file path/dirty state, caret position, detected language, ready LSP server names, diagnostics, selection count, numeric prefix, pending key sequence, and buffer identity/count.
+Builtins are `:tabs`, `:battery`, `:shell`, `:mode`, `:path`, `:position`, `:language`, `:lsp`, `:diagnostics`, `:selections`, `:count`, `:pending`, and `:buffer`, in either bar. They provide tab titles, battery charge, running shell command/spinner, mode, file path/dirty state, caret position, detected language, ready LSP server names, diagnostics, selection count, numeric prefix, pending key sequence, and buffer identity/count.
 
 A bar with no visible content consumes no row. For example, `config.bar.top = { left: [], center: [], right: [] }` removes the top bar. A bar whose only visible content is `:tabs` is hidden with a single tab, whether above or below the workspace. Narrow layouts first omit inactive tabs, then optional segments from group ends to avoid overlap; the active tab drops decorations before its title is clipped. Commands and buffer searches use floating input; operation feedback uses a bottom-right popup. Neither reserves a footer row.
 
@@ -160,6 +160,8 @@ Any other segment name is a custom named value, such as `:build_status`. Set ini
 
 Move `:battery` to any anchor group or remove it from both bars to stop battery collection. A nonempty `config.labels[:battery]` or plugin value explicitly overrides the native text and pauses collection; clearing that value restores native readings. Other custom live values use [`editor.label(name, text)` or asynchronous plugin updates](plugins.md#named-label-updates). Configuration runs once at startup; there are no render callbacks.
 
+`:shell` shows the pending `:!COMMAND` abbreviation and animated spinner, and hides when idle. It defaults to the right of `:battery`; move it to any anchor group or omit it without affecting command execution. A nonempty label named `shell` overrides the builtin display; clearing it restores the running indicator.
+
 ### Command and search popup anchors
 
 Configure the two input windows independently: