feat: support configurable tabline status label

src/ruby_config.rb

@@ -16,6 +16,7 @@ module Vamp
       @file_picker_view = "tree"
       @file_explorer_view = "tree"
       @clipboard_mode = "system"
+      @tabline_label = ""
       @diff_context_lines = 10
       @diff_expand_lines = 15
     end
@@ -62,6 +63,12 @@ module Vamp
       @clipboard_mode = nonempty_string!(mode, "clipboard mode")
     end
 
+    # @param text [String] plain text displayed at the right of the tab line; empty clears it
+    # @return [String]
+    def tabline_label=(text)
+      @tabline_label = Vamp.string!(text, "tabline label")
+    end
+
     # @param lines [Integer] nonnegative context lines around each diff change
     # @return [Integer]
     def diff_context_lines=(lines)
@@ -104,7 +111,7 @@ module Vamp
     def response
       { "version" => 1, "type" => "config", "plugins" => @plugins, "lsp" => lsp_options, "bindings" => @bindings,
         "leader" => @leader, "file_explorer_side" => @file_explorer_side, "file_picker_view" => @file_picker_view,
-        "file_explorer_view" => @file_explorer_view, "clipboard_mode" => @clipboard_mode,
+        "file_explorer_view" => @file_explorer_view, "clipboard_mode" => @clipboard_mode, "tabline_label" => @tabline_label,
         "diff_context_lines" => @diff_context_lines, "diff_expand_lines" => @diff_expand_lines }
     end
 
@@ -203,7 +210,7 @@ module Vamp
     attr_reader :path
     # @return [Integer] positive invocation ID
     attr_reader :request_id
-    # @return [Array<Hash{String => String}>] queued insert/replace/message effects
+    # @return [Array<Hash{String => String}>] queued text and presentation effects
     attr_reader :effects
 
     # @param context [Hash{String => String, Integer, nil}] primary caret/document snapshot
@@ -237,6 +244,12 @@ module Vamp
       queue("message", text)
     end
 
+    # @param text [String] plain text displayed at the right of the tab line; empty clears it
+    # @return [nil]
+    def tabline_label(text)
+      queue("tabline_label", text)
+    end
+
     private
 
     # @param context [Hash{String => String, Integer, nil}]
@@ -281,7 +294,7 @@ module Vamp
       raise ArgumentError, "context buffer_id and revision must be nonnegative integers"
     end
 
-    # @param type [String] insert, replace, or message
+    # @param type [String] insert, replace, message, or tabline_label
     # @param text [String]
     # @return [nil]
     def queue(type, text)