[codex] docs: pin AGENTS.md packaging names

[DhyeyMavani2003]

Summary

• add a packaging section to AGENTS.md with the current installer script locations
• document GOOSE_BIN_DIR as the installer env var used by both install scripts
• list the five current native npm binary packages under ui/goose-binary/

Why

The issue body references stale line numbers and examples that do not exist on current main, but it points at a real maintenance problem: AGENTS.md did not include the current packaging/install names that are easy to copy incorrectly.

This change puts the repo-backed ground truth directly in AGENTS.md so future edits have the right installer env var and native package names in one place.

Impact

• contributors and coding agents have the current installer/package names in the repo's main instructions file
• future docs or rename edits are less likely to drift toward stale package scopes or env vars

Testing

• git diff --check

Closes #8226