docs(kits): write the Notes entries for accepted divergences

One PR covering the #2974 Notes candidates: no deploy-time status surface, no `billingRequired` equivalent, `NODE_PATH` rename, the `ext-` to `kit-` topic rename, plus whatever the decision issues rule as accepted.

Also: kits do not fail at startup on missing config the way the extensions' `validateRequiredEnvVars()` did - required-param presence and bound secrets are enforced by the Firebase CLI at deploy time via `firebase-functions/params` instead, so this is a relocation of validation, not a loss. The remaining conditional-combination gap is tracked in #3022.

Ledger: #2974.