docs(core): stop showing flattenStandardHeader on set-cookie

[dinwwwh]

Summary

Updated the documentation example for mergeStandardHeaders and flattenStandardHeader functions to better illustrate how these utilities handle multi-value headers.

Changes

• Modified the example to demonstrate merging of the vary header across multiple objects, showing how it correctly combines values into an array
• Updated the first input object to include vary: 'accept' to show the merge behavior
• Changed the second input object's vary value from 'accept' to 'accept-encoding' to demonstrate combining different values
• Updated the expected output to show vary as an array ['accept', 'accept-encoding'] instead of a single string
• Changed the final example from demonstrating set-cookie flattening to vary flattening, providing a clearer illustration of the flattenStandardHeader function with the multi-value header

Details

These changes clarify how the header merging functions handle headers that can have multiple values, making the documentation more accurate and helpful for users understanding the behavior of these utilities.

https://claude.ai/code/session_016RHRvK3Kt3oPLgn8Tmk85r

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commit: b7d6289

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[codspeed]

Merging this PR will not alter performance

⚠️ 5 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• json 10KB
• json 10KB
• octet stream 10KB
• blob 10KB
• form data 10KB

ℹ️ 16 benchmarks have no flame graph

The flamegraph could not be generated because too much time was spent in runtime internals, making the visualization not useful for performance analysis.

• form data 10KB
• json 10KB
• blob 10KB
• blob 10KB
• octet stream 10KB
• form data 10KB
• blob 10KB
• octet stream 10KB
• url search params 10KB
• event stream 10KB
• …and 6 more

✅ 26 untouched benchmarks
⏩ 108 skipped benchmarks¹

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_{Comparing claude/brave-pasteur-e7z0fk (b7d6289) with main (31a8ef3)}

Footnotes

1. 108 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[pullfrog]

✅ No new issues found.

Reviewed changes — a docs-only update to the "Header helpers" example in packages/core/README.md.

• flattenStandardHeader now demonstrated on vary — the example adds vary: 'accept' / vary: 'accept-encoding' to the inputs, documents the merged output as ['accept', 'accept-encoding'], and flattens it to 'accept, accept-encoding'. I traced both functions: mergeStandardHeaders concatenates duplicate keys via toArray (utils.ts:167) and flattenStandardHeader joins arrays with ', ' (utils.ts:76), so the documented result is exact.
• Dropping the set-cookie flattening demo — using set-cookie for flattenStandardHeader was misleading (Set-Cookie is not a comma-joinable list), so vary is a genuinely better illustration.

The omitted warning: undefined in the output comment is intentional — it demonstrates that undefined values are dropped.

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