[P1][Carousel] Build narrative-first carousel planning, semantic slide primitives, deterministic rendering, and slide-level revisions

[Ankit6149]

Parent epic

#151

Product outcome

SignalFlow can create swipe/carousel posts as structured sequential narratives rather than as a loose array of generated images.

Canonical docs

• docs/MEDIA_INTELLIGENCE_AND_CREATIVE_PRODUCTION.md
• docs/CREATIVE_MEDIA_DOMAIN_CONTRACTS.md

Core model

Implement CarouselCompositionPlan with stable slide identities and semantic roles.

Suggested semantic roles:

HOOK
STATEMENT
PROBLEM
INSIGHT
PROCESS
SCREENSHOT
DIAGRAM
COMPARISON
BEFORE_AFTER
METRIC
QUOTE
LIST
TIMELINE
CODE
CLOSING
CTA

Rendering principle

AI plans:

• narrative sequence;
• slide copy;
• evidence/visual binding;
• semantic layout intent.

Deterministic renderer handles:

• typography;
• spacing;
• brand treatment;
• screenshot/image placement;
• dimensions;
• accessible hierarchy;
• final PNG/PDF/document output as required by destination capability.

Do not rely on image generation to render seven typography-heavy slides consistently.

Initial slide primitives

Examples:

HookSlide
StatementSlide
ProblemSlide
ScreenshotSlide
DiagramSlide
FeatureSlide
ComparisonSlide
BeforeAfterSlide
MetricSlide
ListSlide
ProcessSlide
TimelineSlide
CodeSlide
QuoteSlide
ClosingSlide
CTASlide

Revision behavior

Natural-language edits should be surgical:

• "Slide 4 is too technical" → revise slide 4 only;
• "move slide 5 before slide 3" → reorder stable slide IDs;
• "use screenshot B on slide 6" → change visual binding only;
• "make body text smaller" → presentation change without rewriting meaning.

Acceptance criteria

• Carousel is a canonical structured composition, not only rendered image files.
• Stable slide IDs survive edits/reordering where identity is unchanged.
• At least six semantic slide primitives render consistently.
• At least one real 5–8 slide narrative is generated from a ContentPiece/MediaRequirement.
• Source evidence/asset bindings remain traceable per slide.
• Slide-level revisions do not unnecessarily regenerate the whole carousel.
• Text overflow, crop and readability checks exist.
• Aspect-ratio/platform output is explicit.
• Reference-only/private assets cannot be bound into final slides contrary to [P0][Media Intent] Add AssetRole, AssetUsePolicy, immutable media lineage, and intent resolution #179.
• Exact rendered carousel revision is reviewable/approval-bound.
• Publication uses the exact approved slide/render revision.

Non-goals

• no Canva replacement;
• no giant visual-template marketplace;
• no freeform vector editor requirement;
• no generated-image typography dependency.

Definition of done

Close only when a user can request or accept a carousel recommendation, review the sequence, revise individual slides naturally, and approve a professional deterministic final carousel with preserved source/asset/provenance state.