Describe the new case format on the public guides (#252)

* Describe the new case format on the public guides

The guides still described the old case: thesis, framework, burden of
proof, contentions with warrants and impacts, and a predicted opponent
case. Generate now writes an opening, arguments (point, explanation,
evidence, why it matters), "If they say… we answer…" replies, a closing
line and sources (#244). The copy changes in seo_guides.py, seo_answers.py
and the PAGES meta in generate_seo_content.py, and the pages and llms.txt
are regenerated from them. The LD, PF, Policy and weighing format guides
are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Match the case guide to the shipped R2: no new arguments, five or six If they say blocks

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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: Programcode