Fix validation errors in view_task_steps(), tool methods, and type coercion

[Vvkmnn]

Fixes #1093 and #1094.

Summary

Seven bugs across type models and resource methods that cause crashes or produce invalid data.

Changes

Type validation (#1093)

• Content2 model (types/task.py): requires_confirmation changed from bool to Union[bool, str]; tool_run_state, tool_config, action_details, params, original_message_ids made Optional — fixes view_task_steps() ValidationError on tool-run responses
• update_params() (resources/tool.py): strip required from property dicts before adding to params_schema["properties"] — JSON Schema requires required as a top-level array, not a boolean inside properties
• PythonCodeTransformation (types/transformations.py): add model_validator to coerce packages string to list — platform API rejects strings with must be array validation error

Resource methods (#1094)

• create_tool() (resources/tools.py:52): uuid.uuid4() → str(uuid.uuid4()) — fixes TypeError: Object of type UUID is not JSON serializable (async version already correct)
• add_tool() (resources/agent.py): guard against None actions on fresh agents, expose action_behaviour parameter ("always-ask" | "never-ask" | "agent-decide")
• remove_tool() (resources/agent.py): guard against None actions
• update_transformations() (resources/tool.py): fetch and include current params_schema in bulk_update body — prevents silent schema erasure when updating transformations after params

Testing

• All 46 existing unit tests pass
• 18/18 end-to-end tests against live API (Content2 parsing, UUID serialization, null-safe add/remove_tool, action_behaviour, params schema validity, schema preservation, packages coercion, view_task_steps with tool-run responses)