Fixes Perplexity research role failing with 'tool-mode object generation' error
The hardcoded 'tool' mode was incompatible with providers like Perplexity that support structured JSON output but not function calling/tool use
Using 'auto' mode allows the AI SDK to choose the best approach for each provider
Replace 🟢, 🟡, 🔴 emojis with ● character in getComplexityWithColor function
Update corresponding unit tests to expect ● instead of emojis
Improves UI continuity
