fix(fetch): guard stream close after cancellation

[mcollina]

This relates to...

Fixes #5715.

Rationale

ReadableStreamFrom defers closing its controller after an async iterator finishes. If the consumer cancels while iterator.next() is still pending, the delayed close runs against an already-closed controller and throws an uncatchable ERR_INVALID_STATE.

Changes

Features

N/A

Bug Fixes

• Ignore the recognized already-closed controller errors when cancellation wins the race with the delayed close.
• Re-throw unexpected controller errors.
• Add a deterministic regression test that cancels while iterator.next() is in flight.

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented (not applicable)
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.48%. Comparing base (5033aa1) to head (824414c).

Files with missing lines	Patch %	Lines
lib/core/util.js	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5716      +/-   ##
==========================================
+ Coverage   93.47%   93.48%   +0.01%     
==========================================
  Files         110      110              
  Lines       38906    38916      +10     
==========================================
+ Hits        36366    36380      +14     
+ Misses       2540     2536       -4     

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