fix(runtime): honor DataView offset and length in TextDecoder.decode

[HiteshShonak]

This Pull Request fixes/closes #4767.

It changes the following:

• Updates TextDecoder.decode for DataView inputs to apply the view window (byteOffset + byteLength) instead of decoding the full backing ArrayBuffer.
• Adds checked conversion for DataView offset/length and returns RangeError if values exceed addressable size.
• Adds a regression test to verify new DataView(buffer, 1, 2) decodes only that slice (expected "CE").

Testing:

• cargo test -p boa_runtime text::tests — 23 passed, 0 failed
• cargo fmt --all — passed

Repro from issue now returns "B" instead of "BB":

• new TextDecoder().decode(new DataView(Uint8Array.of(0x42, 0x42).buffer, 1))

Spec reference:
https://encoding.spec.whatwg.org/#dom-textdecoder-decode

[Copilot]

Pull request overview

This PR fixes TextDecoder.decode behavior for DataView inputs so decoding respects the view’s byteOffset/byteLength window (instead of decoding the full underlying ArrayBuffer), aligning behavior with the WHATWG Encoding spec and resolving #4767.

Changes:

• Apply DataView’s byteOffset + byteLength slice when decoding in TextDecoder.decode.
• Add checked conversion from u64 to usize for DataView offset/length, returning a RangeError when values are not addressable on the platform.
• Add a regression test validating that new DataView(buffer, 1, 2) decodes only that slice (expects "CE").

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
core/runtime/src/text/mod.rs	Updates TextDecoder.decode to compute and apply the correct byte range for DataView inputs, with usize conversion checks.
core/runtime/src/text/tests.rs	Adds a regression test ensuring DataView offset/length are honored during decoding.

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[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,079	50,079	0
Ignored	2,072	2,072	0
Failed	812	812	0
Panics	0	0	0
Conformance	94.55%	94.55%	0.00%

Tested main commit: 07ebe591c721307f110cc4b082f03d7d62f4a352
Tested PR commit: 2b3343037aba3ca5df2af8944150699daa2408d6
Compare commits: 07ebe59...2b33430

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.72%. Comparing base (6ddc2b4) to head (2b33430).
⚠️ Report is 899 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5172       +/-   ##
===========================================
+ Coverage   47.24%   59.72%   +12.47%     
===========================================
  Files         476      580      +104     
  Lines       46892    63261    +16369     
===========================================
+ Hits        22154    37782    +15628     
- Misses      24738    25479      +741     

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[jedel1043]

Thanks!