feat: migrating from tsup to tsdown

[jaredwray]

Please check if the PR fulfills these requirements

• Followed the Contributing guidelines and Code of Conduct
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
feat: migrating from tsup to tsdown

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (6e279c5) to head (cb104fc).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #130   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            8         8           
  Lines          477       477           
  Branches        95        95           
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  Hits           477       477           

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[gemini-code-assist]

Code Review

This pull request transitions the project from tsup to tsdown for building, updates package.json to support modern export maps, and enforces stricter TypeScript rules including isolatedDeclarations. The review identifies an invalid TypeScript version (^6.0.2) in the dependencies and suggests re-enabling the --clean flag in build scripts to prevent the inclusion of stale artifacts in the distribution folder.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Point top-level types at CJS-compatible declarations

Changing types to dist/index.d.mts makes CommonJS TypeScript consumers that still use moduleResolution: "node"/"node10" resolve ESM declarations instead of the CJS branch, because those resolvers ignore conditional exports typing and read only the top-level types field. In that setup, import = require('@hyphen/sdk') and similar CJS typing patterns no longer align with the runtime require entry even though exports.require.types is present, so this should point to a CJS-compatible declaration (or a compatibility .d.ts shim) to avoid a regression for legacy CJS TS projects.

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