feat: guided tours / learning paths

[rajnavakoti]

Description

Auto-generated walkthroughs through the KB, ordered by dependency. Per-persona paths that guide a new user through the most important entities in a logical order. Natural extension of persona-based evals.

Acceptance Criteria

• Tour generated per persona (developer, architect, PO, new-joiner)
• Each tour is an ordered list of entities with transition narration
• Tour respects dependency order (understand X before Y)
• Viewer page with step-by-step navigation
• Tours regenerated when KB is updated

Out of Scope

• Interactive quizzes within tours
• Custom tour creation by users