[Epic] Restore installation, sign-in, activation, and runtime incidents quickly

## Problem statement

Installation, authentication, activation, streaming, architecture, and runtime failures prevent users from accessing the existing product. These incidents require durable ownership and reusable diagnostics.

## Outcome

User-impacting availability incidents are detected, triaged, mitigated, and resolved within defined service expectations.

## Goals

- Centralize active installation, sign-in, activation, and runtime support work
- Improve diagnostic evidence and reproduction paths
- Identify recurring patterns and eliminate systemic causes
- Maintain supported desktop, WSL, Codespaces, OS, and architecture behavior

## Non-goals

- Treating net-new product capabilities as incidents
- Hiding unsupported-environment errors

## Success criteria

- [ ] Incidents have actionable diagnostics and ownership
- [ ] Recurring failures produce product fixes or support automation
- [ ] Supported environments remain installable and responsive

## Dependencies

Client runtimes, authentication, packaging, telemetry, support, and release infrastructure.

No files, tests, or entry points are named. Begin by mapping the active installation, sign-in, activation, streaming, and runtime support work across the listed dependencies, then identify owners and reproduction paths. Done means incidents have actionable diagnostics and ownership, recurring failures produce fixes or automation, and supported environments remain installable and responsive.

Written by the indexing model from the issue text.