Docs

• Builtins: manpage-style reference for POSIX, compatibility, and Rush extension builtins.
• Advanced features: adaptive themes, terminal protocols, and interactive UX.
• Writing completions: build command completion manifests and dynamic provider functions.
• Completion manifest schema: JSON schema reference for structured completion manifests.
• Conformance policy: how Rush chooses behavior when POSIX, Bash, and system shells disagree.
• Compatibility notes: known differences from common shell reference points.
• Configuration: prompt and startup configuration.