docs: plan a unified settings hierarchy

[Codename-11]

What changed

• inventories Instance Admin, Mission Control/global settings, and workspace settings by actual ownership scope
• proposes one Settings system with Personal, Workspace, and Instance scope switching
• records a phased migration plan, acceptance criteria, and prioritized P0/P1/P2 findings
• documents the browser-capture blocker and the required visual/accessibility walkthrough

Why

Forge currently presents personal, workspace, cross-workspace, and instance configuration through three shells with ambiguous labels and scope jumps. The review aligns navigation with the existing user/workspace/instance ownership model before implementation begins.

Important findings

• auto-dispatch fall-through is described but cannot be changed in the UI
• global runtime cards can route through a workspace where runtime detail returns 404
• instance-wide authentication appears under Account settings
• Mission Control names both the cross-workspace home and an in-workspace activity panel

Validation

• code and route inventory completed against v0.14.0
• document links and code anchors reviewed
• no screenshot-backed visual or WCAG claims: in-app Browser was unavailable and Chrome remote debugging was disabled

This is a planning PR. It intentionally does not implement or deploy the proposed redesign.