Resume Task Agent Approval Request

Resume a paused Task Agent run after an approval decision. Resume reuses the original TaskAgentRun ID, ADK session ID, ADK session owner key, and pinned TaskAgent revision. Approved requests allow the exact approved tool call once. Rejected requests are resumable only when the matched action control uses `return_rejection_to_model`, in which case the service resumes ADK with a controlled function response for the original function call. Example stream after an approval is granted: the approved tool executes and its `tool_result` is emitted directly (the proposing `tool_call` was already shown via the original run's `approval_required` event, so it is not repeated), followed by any further reasoning, the terminal `formatted_output`, and `done`: ``` data: {"event_type": "tool_result", "tool_name": "sheets_spreadsheets_values_append", ...} data: {"event_type": "tool_call", "tool_name": "draft_support_reply", ...} data: {"event_type": "formatted_output", "content": "Logged — ticket TCK-4821 is marked resolved in the tracker.", ...} data: {"event_type": "done", "metadata": {"run_id": "...", "session_id": "...", ...}} ``` Terminal `done` and `error` SSE events include fallback metadata when a run is known: `used_fallback_model` and `fallback_model_id`. Terminal `error` events also include stable `error_code` and `termination_reason` values. Current error codes are `CONTEXT_WINDOW_EXCEEDED`, `INTEGRATION_NOT_CONNECTED`, `INTEGRATION_REAUTH_REQUIRED`, `INTEGRATION_AUTH_REQUIRED`, `UNSUPPORTED_INTEGRATION_TYPE`, `INSUFFICIENT_CREDITS`, `APPROVAL_CAPTURE_FAILED`, `FORMATTER_FAILED`, `FORMATTER_EMPTY_OUTPUT`, `TASK_AGENT_NOT_FOUND`, and `EXECUTION_ERROR`.