Add comprehensive installation walkthroughs for macOS, Windows, Linux (Ubuntu/Debian,
Fedora/RHEL, Arch, nvm), and Docker. Each OS section follows a consistent numbered
step-by-step flow covering dependency install, verification, GSD install, provider
setup, first launch, and verification. Includes download links, platform-specific
tips, and a quick troubleshooting table.
Delete the Anthropic OAuth module, remove it from the built-in provider
registry, strip the OAuth client branch from the Anthropic streaming
provider, and replace the daemon orchestrator's token refresh with a
simple ANTHROPIC_API_KEY requirement.
Anthropic access is now API key or local Claude Code CLI only.
Closes#3952
Split flat docs/ into user-docs/ (guides, config, troubleshooting) and
dev/ (ADRs, architecture, extension guides, proposals). Updated
docs/README.md index to reflect new paths.
