ui: show competitors and grounding sources in tabbed sidebar view

[arberx]

Problem

The run detail sidebar currently shows "Who was cited" with grounding source domains (e.g. techloy.com, apollotechnical.com). Users expect to see the actual competitor companies that AI recommended in its answer (e.g. Accenture, Deloitte, Capgemini).

These are two different data points:

• Grounding sources — URLs the provider referenced to build its answer (already stored as groundingSources)
• Recommended competitors — company/brand names extracted from the response text (stored as recommendedCompetitors per provider result)

Both are valuable but serve different purposes:

• Competitors → "who AI picks instead of you"
• Grounding sources → "what content is feeding the AI recommendations" (actionable for link-building / listicle placement)

Proposed Solution

Replace the single "Who was cited" sidebar with a tabbed view:

1. Competitors tab (default) — aggregated competitor names with mention counts across all providers/queries
2. Sources tab — grounding source domains as currently shown

Default to the Competitors tab since that is the primary insight users care about during competitive analysis.

Data Availability

recommendedCompetitors is already extracted per provider result by the batch analysis LLM (fixed in #193/#194). The API already returns this data — the UI just needs to surface it.