Switch to ESM

[carlos-poly]

Note

Medium Risk
Medium risk because this is a breaking packaging change (ESM + exports + .js specifiers) that can affect downstream consumers and build/test resolution, despite minimal runtime logic changes.

Overview
This PR converts the SDK from CommonJS to ESM/NodeNext: package.json adds type: module and an exports map, tsconfig.json switches to module/moduleResolution: nodenext, and the build no longer forces --module commonjs.

All internal imports/exports are updated to use explicit .js extensions (including tests), and the HMAC signer switches from crypto.createHmac default import to node:crypto’s createHmac. It also removes the tslib dependency and bumps the package version to 1.0.0.

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[carlos-poly]

• Switch to ESM #7 👈 (View in Graphite)
• main

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