v0.1.3

Pure additive release that re-exports two helpers from the package root so adopters no longer have to import them through a deep internal path:

• validateMessage(raw) runs the canonical MessageEnvelopeSchema parse plus the intent-specific payload schema. Receivers building from scratch were either re-implementing the schema check or pulling from @adastracomputing/ink/dist/models/intent.js, which is not a stable surface. The implementer-guide at https://ink.tulpa.network/guides/implementing-a-receiver/ documented this helper as if it were already exported; this release makes that documentation accurate.
• decodeEncryptionKeyMultibase(multibase) is the companion to the already-exported decodePublicKeyMultibase. The former handles X25519 keys (the Agent Card encryption-key prefix); the latter handles Ed25519. The encrypted-intents guide tells adopters to decode an Agent Card's publicKeyMultibase for use with encryptInkPayload, which expects hex; without the X25519 decoder exported, adopters had to inline the multicodec strip themselves.

Also re-exports the MessageEnvelope type and the MessageEnvelopeSchema constant so adopters can type their parser surface against the canonical schema. No wire-level changes. No behavior changes inside the existing functions. Receivers on 0.1.2 work unchanged on 0.1.3.

This release publishes under the npm next dist-tag per the pre-1.0 policy.