add taskcreate tool use formatter

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

@@ -312,6 +312,23 @@ def format_taskupdate
               "TASKUPDATE ##{input[:taskId]} → #{input[:status]}"
             end
 
+            # Formats a TaskCreate tool-use line.
+            #
+            # Input fields:
+            #   :subject (String) – title of the task to create   [required]
+            #
+            # Output: "TASKCREATE <subject>", with :subject truncated to
+            # TRUNCATE_LIMIT chars.
+            #
+            # Examples:
+            #   TASKCREATE Run formatter stress test
+            #   TASKCREATE Review multiline edit output in tmp/formatter_st...
+            #
+            #: () -> String
+            def format_taskcreate
+              "TASKCREATE #{truncate(input[:subject])}"
+            end
+
             #: () -> String
             def format_unknown
               "UNKNOWN [#{name}] #{input.inspect}"

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

@@ -378,6 +378,26 @@ class ToolUseTest < ActiveSupport::TestCase
               assert_equal "TASKUPDATE #1 → completed", output
             end
 
+            # format_taskcreate
+
+            test "format_taskcreate renders the subject" do
+              tool_use = ToolUse.new(name: :taskcreate, input: { subject: "Run formatter stress test" })
+
+              output = tool_use.format
+
+              assert_equal "TASKCREATE Run formatter stress test", output
+            end
+
+            test "format_taskcreate truncates the subject" do
+              long = "a" * (ToolUse::TRUNCATE_LIMIT + 10)
+              truncated = "#{"a" * (ToolUse::TRUNCATE_LIMIT - 3)}..."
+              tool_use = ToolUse.new(name: :taskcreate, input: { subject: long })
+
+              output = tool_use.format
+
+              assert_equal "TASKCREATE #{truncated}", output
+            end
+
             test "format calls format_unknown for unknown tool" do
               tool_use = ToolUse.new(name: :unknown_tool, input: { arg: "value" })