add taskupdate tool use formatter

lib/roast/cogs/agent/providers/claude/tool_use.rb

@@ -293,6 +293,25 @@ def format_agent
               details.empty? ? "AGENT #{description}" : "AGENT #{description} (#{details})"
             end
 
+            # Formats a TaskUpdate tool-use line.
+            #
+            # Input fields:
+            #   :taskId (Integer) – id of the task to update   [required]
+            #   :status (String)  – the task's new status      [required]
+            #
+            # Output: "TASKUPDATE #<taskId> → <status>" — the id is prefixed with
+            # "#" and joined to the status with " → ". Both fields are always
+            # shown and neither is truncated.
+            #
+            # Examples:
+            #   TASKUPDATE #1 → completed
+            #   TASKUPDATE #2 → in_progress
+            #
+            #: () -> String
+            def format_taskupdate
+              "TASKUPDATE ##{input[:taskId]} → #{input[:status]}"
+            end
+
             #: () -> String
             def format_unknown
               "UNKNOWN [#{name}] #{input.inspect}"

test/roast/cogs/agent/providers/claude/tool_use_test.rb

@@ -368,6 +368,16 @@ class ToolUseTest < ActiveSupport::TestCase
               assert_equal "AGENT #{truncated} (#{long})", output
             end
 
+            # format_taskupdate
+
+            test "format_taskupdate renders the task id and status" do
+              tool_use = ToolUse.new(name: :taskupdate, input: { taskId: 1, status: "completed" })
+
+              output = tool_use.format
+
+              assert_equal "TASKUPDATE #1 → completed", output
+            end
+
             test "format calls format_unknown for unknown tool" do
               tool_use = ToolUse.new(name: :unknown_tool, input: { arg: "value" })