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

[cabljac]

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.