Design pillar: consent mode / GDPR-safe deferred load

[productdevbook]

Loader must not fire on module import. Consumers gate it behind CMP (OneTrust, Cookiebot, Iubenda, etc.).

Evidence

• `Add support for GDPR adamsoffer/react-hubspot#6` — "Add support for GDPR" Add support for GDPR adamsoffer/react-hubspot#6
• `Allow European configuration aaronhayes/react-use-hubspot-form#44` — "Allow European configuration" Allow European configuration aaronhayes/react-use-hubspot-form#44
• `dansmaculotte/nuxt-zendesk` — GDPR script-defer option (prior art)
• `Add support for delaying the intercom initialize script to avoid performance issues devrnt/react-use-intercom#237` — "Add support for delaying the intercom initialize script" Add support for delaying the intercom initialize script to avoid performance issues devrnt/react-use-intercom#237
• `Anyway this package can be lazy loaded? devrnt/react-use-intercom#364` — "Anyway this package can be lazy loaded?" (Lighthouse "facade" pattern) Anyway this package can be lazy loaded? devrnt/react-use-intercom#364

Contract

1. `load()` must be explicitly invoked — nothing happens on import.
2. `load({ defer: "idle" | "interaction" | "manual" })` strategies:
   • `idle` (default) — `requestIdleCallback` with polyfill
   • `interaction` — load on first `pointerdown` / `scroll` / `keydown`
   • `manual` — user calls `resume()` after consent
3. `region: "eu" | "us"` flag for HubSpot (`js-eu1.hs-scripts.com`), Zendesk (EU subdomain), Intercom (`api-iam.intercom.io` regional).
4. Integrations doc: OneTrust, Cookiebot, Iubenda, Tarteaucitron snippets.
5. Partytown integration recipe (see `Run Intercom through Partytown devrnt/react-use-intercom#741`).

[productdevbook]

Implemented in this commit