Propagate response_fn / get_all_responses_fn through Discover pipeline

[hemanth-asirvatham]

Motivation

• Ensure custom per-prompt or driver overrides (response_fn / get_all_responses_fn and other runtime kwargs) passed into Discover.run actually reach the downstream stages (Codify, Compare, Bucket, Classify) so custom handlers are honored end-to-end.
• Note: the core helper get_all_responses already implements precedence, validation and behavior for custom drivers and response functions, so the pipeline should forward the kwargs rather than swallow them.

Description

• Forward **kwargs from Discover.run into internal stage calls by adding **kwargs when calling coder.run, cmp.run, buck.run, clf.run in src/gabriel/tasks/discover.py so options such as response_fn and get_all_responses_fn are propagated.
• No change to get_all_responses itself; it continues to validate custom drivers (requires prompts/identifiers) and to make get_all_responses_fn take precedence over response_fn when both are supplied.
• Small, targeted change confined to src/gabriel/tasks/discover.py to unblock end-to-end custom response overrides.

Testing

• No automated tests were executed for this change.

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Codex Task

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