Add a Cited pages tab to Prompt Explorer

[bensenescu]

Problem

Prompt Explorer returns citations per model, but they are buried inside each response. Users need one scan-friendly view of which pages were cited across the selected models.

Implementation check

Checked main at fec642a0:

• src/server/features/ai-search/services/promptExplorer.ts already extracts and deduplicates citation URL, domain, title, and brand match per model.
• src/types/schemas/ai-search.ts already exposes the citation data needed by the UI.
• src/client/features/ai-search/PromptExplorerPage.tsx and components/PromptExplorerResults.tsx own the post-search layout and current inline citation lists.

No provider or schema change is needed for the first pass.

Suggested direction

Add Responses and Cited pages tabs after a search. Aggregate citations client-side by URL and show source, citing models, brand match, and citation count. Reuse existing citation-table patterns from Brand Lookup where practical.

Contributor fit

Good for a frontend TypeScript contributor comfortable with table state and a small aggregation helper. No DataForSEO work is expected.

Acceptance criteria

• Prompt Explorer results include a clearly labeled Cited pages view.
• URLs are deduplicated across models and show which models cited each page.
• Brand matches are preserved and empty/partial citation states are explicit.
• The existing response comparison remains available.
• Tests cover URL dedupe, multi-model attribution, and brand-match preservation.

Product mockup