Summary

Foundation change for the audience SDK: adds the shared IdentityType union and narrows the web SDK to use it.

1. IdentityType const + type — shared identity type in @imtbl/audience-core matching the backend's OAS enum (passport | steam | epic | google | apple | discord | email | custom). Exported as both a const object (for runtime values) and a type alias (for parameter typing).
2. Narrowed identify() and alias() params — identify()'s positional string arg changes type from string → IdentityType. alias() parameter shape also changes from { uid, provider } → { id, identityType } to match backend wire field names (fromId/fromType/toId/toType).

Commits

1. feat(audience-core): export IdentityType const + type — the union + JSDoc pointer to the backend OAS
2. feat(audience)!: use IdentityType for identify() and alias() params — BREAKING, see below

⚠️ Breaking change

alias() now takes { id, identityType } objects instead of { uid, provider }. identify()'s positional string arg keeps the same name but changes type from string → IdentityType.

// before
audience.identify('user-123', 'passport', traits);
audience.alias(
  { uid: 'steam-id', provider: 'steam' },
  { uid: 'passport-id', provider: 'passport' },
);

// after
audience.identify('user-123', 'passport', traits);                  // typed
audience.alias(
  { id: 'steam-id', identityType: 'steam' },
  { id: 'passport-id', identityType: 'passport' },
);

Nothing from this package has been published externally, so the rename is safe to land — but calling it out so reviewers can push back if they disagree.

Tickets

• Partially addresses SDK-74 (Identity types should be typed and match backend enums) — web SDK half only. Pixel half tracked as SDK-77.
• The rename is broader than SDK-74 strictly required. SDK-74 asked for the existing string params to be narrowed; this PR also renames uid/provider → id/identityType for parity with backend wire field names. Flagging for review.

Scope

This branch previously also contained commits for a TransportResult refactor, error propagation, and an AudienceError surface on Audience.init(). Those have been split out based on reviewer feedback that the transport/queue/errors layer needs deeper design work — unified error sink in core rather than sdk, collapsing the Transport interface, fixing a partial-success silent-drop in MessageQueue.flush, and wiring onError through pixel. Landing identity types first unblocks the demo PR.

Test plan

• pnpm --filter @imtbl/audience-core --filter @imtbl/audience --filter @imtbl/pixel test — 203 tests pass (90 core + 49 sdk + 64 pixel)
• CI green

What's next

• Follow-up PR: audience transport/errors refactor.
• Demo PR (feat/audience-web-sdk-demo) builds the interactive demo page on top of this branch once it lands.

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