Record the Runtime Install Policy Module decision and ownership
boundary: install policy projects a pure, typed install plan by
composing artifact placements (ADR-3660) and command text (ADR-0009)
plus per-runtime config intentions, with no filesystem IO; runtime
adapters consume the plan and execute concrete file mutations and
format-specific config rendering. Explicitly records what stays
outside the policy module (TOML/JSON/Markdown serialization, merge
semantics, filesystem effects).
Adds the ADR index row in docs/adr/README.md and a glossary entry in
CONTEXT.md. Leads the installer-refactor chain (#58 -> #60 -> #56).
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
