Build HookFlowVisualizer — scenario-based hook chain animation

[yonatangross]

Context

Phase 3 of docs overhaul. Show what happens when a user runs a dangerous command — visualize the hook chain catching it.

Requirements

• Scenario selector: "dev runs rm -rf /", "dev commits secrets", "agent tries to modify production"
• Animated flow showing: event fires, hook matches, action taken (block/warn/log)
• Step-through mode for tech leads evaluating security
• Shows which of the 104 hooks fire for each scenario

Acceptance Criteria

• 3-5 pre-built scenarios
• Step-through animation with play/pause
• Each step links to the relevant hook reference page
• Embedded on Hooks Overview page