Plumb keep_thinking through renderer factory

[rasdani]

Summary

• adds a generic tri-state keep_thinking argument to create_renderer and create_renderer_pool
• preserves renderer constructor defaults when keep_thinking=None, forces enabled with True, and forces disabled with False
• adds ClientConfig.renderer_keep_thinking and carries it through RendererClient into the shared renderer pool
• raises a clear error when keep_thinking=True is requested for an unsupported renderer instead of adding per-model registry aliases

Test plan

• uv run pytest packages/renderers/tests/test_keep_thinking.py -k 'create_renderer'
• uv run pytest tests/test_renderer_client.py -k 'renderer_client_forwards_keep_thinking or renderer_client_honors_configured_renderer_name or renderer_client_uses_renderer_model_name_override'
• uv run ruff check packages/renderers/renderers/base.py packages/renderers/tests/test_keep_thinking.py verifiers/types.py verifiers/clients/renderer_client.py tests/test_renderer_client.py
• uv run ruff format --check packages/renderers/renderers/base.py packages/renderers/tests/test_keep_thinking.py verifiers/types.py verifiers/clients/renderer_client.py tests/test_renderer_client.py
• git diff --check

Note: uv run pytest packages/renderers/tests/test_keep_thinking.py reaches the new regression and passes 10/11 tests locally, but the existing moonshotai/Kimi-K2.5 tokenizer case fails in this environment because tiktoken is not installed.

Stacked on #1278.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

ClientConfig docs not updated with new field

Low Severity

The new renderer_keep_thinking field is added to ClientConfig in verifiers/types.py, but ClientConfig is explicitly documented in docs/reference.md (lines 754–767) and that documentation is not updated to include the new field. This violates the rule requiring documentation updates when core user-facing functionality described in docs/ is modified.

 

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[hallerite]

I think we should disambiguate between keeping thinking between tool-calls and between user-turns and offer both for any model unconditionally, but have sensible defaults and log a warning if a model does not support it (like Qwen3).

Wdyt?

[hallerite]

Superseded by #1298 (and the underlying renderers PRs #5 / #6). Closing!