[Branch] Animated chat-bubble field exploration

[twblack88]

Context

Exploratory branch for the landing experience (#244). A slow-scrolling field of decorative chat bubbles in the brand palette sits behind the welcome promp, hinting at the breadth of things the agent can do.

Merges into main only if it wins the comparison against 3b (shader) and the safe gradient path.

Approach

• Render a field of decorative chat bubble shapes behind the prompt area using the existing brand color palette.
• Animate them with a slow upward/drifting scroll — subtle, not distracting.
• Likely requires framer-motion (check if already in deps before adding).
• Must not interfere with prompt box interaction or accessibility.

Acceptance criteria

• Feels warm and hinting at conversational capability on desktop.
• Animation is smooth (no jank) and doesn't distract from the prompt.
• Gracefully degrades or pauses if prefers-reduced-motion is set.
• Perf is acceptable on mobile.

Decision point

Once this branch is reviewable alongside #244-3b (shader) and the safe gradient path, pick the winner. If neither beats the safe path on perf/polish tradeoff, this branch is dropped.

Verification

bun run lint
bun run type-check
bun test