Fix output schema names for Literal types

[mindbomber]

Fixes #3357.

Summary

• Make AgentOutputSchema.name() handle typing arguments that are literal values rather than Python types.
• Preserve existing formatting for normal types and generics.
• Add regression coverage for top-level Literal["ok"] and nested list[Literal["ok", "done"]] output types.

Verification

• uv run pytest tests/test_output_tool.py -q
• uv run ruff check src/agents/agent_output.py tests/test_output_tool.py
• uv run ruff format --check src/agents/agent_output.py tests/test_output_tool.py
• git diff --check

[seratch]

resolved by #3358