buffer: use Clamp conversion in Blob slice

[HoonDongKang]

This aligns Blob.prototype.slice() with the File API Web IDL definition:

Blob slice(optional [Clamp] longlong start,
optional [Clamp] longlong end,
optional DOMString contentType);

The start and end arguments should use Web IDL [Clamp] conversion.

This fixes the expected failures in Blob-slice.any.js for fractional start/end values.

Refs: https://www.w3.org/TR/FileAPI/#dfn-Blob

Testing

$ ./node test/wpt/test-blob.js Blob-slice.any.jsFiles: 1/1 ran, 1 passed, 0 skipped, 0 expected failures, 0 unexpected failures, 0 unexpected passesSubtests: 150 passed, 0 skipped, 0 expected failures, 0 unexpected failures, 0 unexpected passes

$ tools/test.py wpt/test-blob[00:00|% 100|+ 1|- 0]: Done

[nodejs-github-bot]

Review requested:

• @nodejs/web-standards

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (0618e9f) to head (6c536b1).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #64739 +/- ##
==========================================
+ Coverage 90.14% 90.15% +0.01% 
==========================================
Files 743 743 Lines 242408 242507 +99 Branches 45656 45776 +120 ==========================================
+ Hits 218520 218643 +123 + Misses 15387 15379 -8 + Partials 8501 8485 -16 

Files with missing lines	Coverage Δ
lib/internal/blob.js	89.86% <100.00%> (ø)

... and 35 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75136/

[HoonDongKang]

This looks like a Jenkins infra failure:
Failed to trigger fanned build in the 2026-07-26 reliability report.
Could someone please rerun CI?

(I accidentally closed the PR, so I reopened it. 🥲)

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75160/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75177/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75186/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75216/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75274/

[nodejs-github-bot]

Landed in a0dd71e