Evaluate brew / multi-channel install options

[Blackman99]

Why

npm global is not enough for some users. Evaluate whether brew (and optionally other channels) reduces install friction without fragmenting support.

Ask

Spike / decide:

1. Homebrew formula or cask feasibility (macOS; Linux brew optional)
2. What else is worth supporting short-term (e.g. npx, scoop) vs defer
3. Ownership: who updates the formula on release

Out of scope for this ticket

Implementing the one-shot npm/script path (separate issue).

Acceptance

• Short write-up in the issue or docs/ with go / no-go per channel
• If go: follow-up issue for the actual formula; if no-go: close with rationale

Deduped: not covered by #62/#63/#64/#76–#83.