[Epic] Replace the static prototype with a real desktop workbench

[KSemenenko]

Problem

The current Uno shell already shows the intended information architecture, but it still uses static sample data and needs tracked work to become a real operator workbench.

Scope

• Preserve the current left navigation, central session surface, right inspector, and agent-builder concepts
• Track file browsing, editor integration, artifacts, logs, and settings workbench features

Out of scope

• Replacing the current shell with a different product layout
• Implementing runtime orchestration or provider adapters directly

Planned child issues

• Turn the existing three-pane shell into the primary workbench
• Add a repository tree with search and open-file navigation
• Embed a Monaco-backed file viewer and diff surface
• Add an artifact dock and runtime console
• Build the unified settings shell

Definition of Done

• The workbench feature issues exist and reference this epic
• The epic preserves the current desktop-first UI direction

Verification

• Child issues reference this epic
• The workbench scope is clearly separated from provider and runtime implementation work