Installer profiles, package manager install, update guidance, and sandbox permissions

Provenance stamp: This issue was triaged on June 13, 2026 as part of the older-than-two-month GitHub issue triage exercise.

Source issues: #25, #140, #466

## Summary

The installation story needs to be easier to understand, easier to update, easier to uninstall, and safer to use in restricted environments. These issues all point to the same gap: users need clear install profiles and a documented operating model for the binary, plugins, skills, daemon, package managers, and sandboxes.

## What the source issues requested

- #25 requested a unified update command or update guidance so the binary and Claude Code plugin do not appear out of sync or confuse users.
- #140 requested package-manager installation, especially Homebrew, and called out clean uninstall as a major reason to support it.
- #466 requested documentation and tests for the permissions Plannotator needs when Claude Code or another tool runs in a sandbox.

## Triage determination

These should be handled together because they are all install lifecycle questions. If package-manager support lands without clear profiles, or sandbox docs land without explaining what the installer writes, users will still see the same confusion from a different angle.

## Acceptance criteria

- Installation docs explain the current responsibilities of the binary, plugin, skills, daemon, and per-runtime command entry points.
- Users can choose or understand profiles such as binary-only, Claude, OpenCode, Pi, Codex, skills-only, and all-in install.
- Update guidance explains what must be updated after a release and what is intentionally version-independent.
- Package-manager installation is supported or explicitly deferred with the remaining blockers listed.
- Uninstall behavior is documented, including files under user config and data directories.
- Sandbox requirements are documented, including filesystem access, local network binding, browser or open command behavior, data directory access, and localhost versus `127.0.0.1`.
- The old source issues can be closed after this replacement issue carries their install and sandbox requirements.