feat: Export endowment factories via sub-path

[sirtimid]

Summary

• Adds @metamask/snaps-execution-environments/endowments sub-path export exposing generic endowment factory modules: timeout, interval, date, textEncoder, textDecoder, crypto, math
• These factories are fully generic (no Snaps-specific coupling) and can be reused by other SES-based projects like ocap-kernel
• Snaps-specific factories (console, network) and types referencing internal Snaps modules are intentionally excluded to keep the public API clean

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Note

Medium Risk
Adds a new public entrypoint via package exports, which can affect downstream bundling/type resolution even though underlying runtime logic is unchanged.

Overview
Introduces a new public subpath export, @metamask/snaps-execution-environments/endowments, to expose the generic endowment factory modules (timeout, interval, date, textEncoder, textDecoder, crypto, math).

Updates packaging and tooling to support this new entrypoint by adding ./endowments to package.json exports, documenting it in the changelog, and excluding src/endowments.ts from Jest/Vitest coverage reporting.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.56%. Comparing base (22f8da9) to head (bf365e7).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3957   +/-   ##
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  Coverage   98.56%   98.56%           
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  Files         428      428           
  Lines       12347    12347           
  Branches     1940     1940           
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  Hits        12170    12170           
  Misses        177      177           

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