Configurable sections (custom names/emoji/order) + interactive TUI

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Let users define their own section names, emoji, and order instead of the fixed 🧠 Needs action / 🚧 In progress / 🚘 Parked / ✅ Done / 📦 Shipped.

Build an interactive bubbletea TUI during sidecar init to pick and reorder sections.

Parked from the sidecar dogfood queue.