Replaces the vague "intro → development → conclusion" guidance in the
generator prompt with an explicit per-slide arc: open with a specific
real urgent problem, develop the idea while creating swipe motivation,
prove with concrete evidence (result/before-after/BTS/learning), and
close with a single specific next action. Includes a slide_count to
role-distribution table (2 through 6+ slides).
Adds a `role` enum field to each slide in the carousel JSON schema
(hook, development, proof, cta) so the structure is enforced via SDK
not just prompt text. Field is additive — handleCarousel still reads
only title/body/image_keywords, so consumers are unaffected.
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