sandbox/ui-baseline-vnext

[lebduska]

Context

Current UI state is accepted as the baseline for further work.

This issue defines a new sandbox stream for interactive UI exploration.
We are NOT continuing any legacy UI or addon architecture work.

Scope

• Single working branch
• Continuous iteration directly in the running app
• Focus on layout, interaction, and mental model
• No requirement to preserve existing UI content

Target mental model

IDE-like workspace:

• Left: context outliner (what matters now)
• Center: workspace with tabs / panels
• Right: contextual help / inspector
• Bottom: prompt bar as a control surface for AI

Constraints

• Do NOT refactor backend or protocol layers
• Do NOT revive legacy UI tasks
• Prefer small, visible changes over abstractions
• This is a sandbox, not a delivery milestone

Definition of success

• App feels like a calm, configurable workspace
• UI can be reshaped freely without fear of breaking commitments