Add interactive flavor events with risk/reward choices

[matalvernaz]

Problem

Flavor events are purely cosmetic text. They're atmospheric but don't affect gameplay, so players learn to ignore them.

Proposal

25% of flavor events are now interactive — they display a gold-bordered event with a clickable action button. Each has a risk/reward outcome:

• Wandering Merchant — Trade 10s of production for a 1.5x-3.5x return
• Mana Surge — 70% chance to gain 30s of production, 30% it fizzles
• Ancient Tome — Summons a random Runestone
• Mysterious Stranger — 60% chance for 60s production bonus, 40% lose 5% Mana
• Crystal Formation — Guaranteed 45s of production
• Spell Echo — Summons a Runestone

Events auto-expire after 30 seconds if not clicked. Results display for 8 seconds then fade.

Accessibility

• Interactive events use role="region" with aria-label="Interactive event"
• Action buttons have descriptive aria-label text
• Results announced via aria-live="polite"
• Gold border + different background color distinguishes them visually