[Repo Assist] feat: add Group 1 AsyncSeq design-parity functions

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Summary

Implements the remaining Group 1 functions identified in the AsyncSeq/TaskSeq design-parity gap analysis (#345), responding to @dsyme's request to "work on group 1".

distinctUntilChangedWith/distinctUntilChangedWithAsync were already added in PR #346. This PR covers everything else in Group 1:

New function(s)	What it does
replicateInfinite value	Infinite sequence of a constant value
replicateInfiniteAsync computation	Infinite sequence via repeated async computation
replicateUntilNoneAsync computation	Emit until computation returns None
firstOrDefault defaultValue	Returns first element or default (wraps tryHead)
lastOrDefault defaultValue	Returns last element or default (wraps tryLast)
splitAt count	Splits into (prefix array, remaining TaskSeq) in a single pass
zipWith mapping / zipWithAsync mapping	Zip two sequences with an inline mapping function
zipWith3 mapping / zipWithAsync3 mapping	Zip three sequences with an inline mapping function
chunkBy projection / chunkByAsync projection	Groups consecutive elements by key
threadState folder state	Streaming stateful map — yields results lazily (like mapFold but lazy)
threadStateAsync folder state	Async variant of threadState

Design notes

• splitAt shares a single enumerator between the prefix array and the rest sequence, following the same single-pass pattern as the existing tryTail. This is safe for the common case of replayable sequences (taskSeq builders, arrays, lists, etc.).
• chunkBy groups consecutive equal-key runs only, unlike groupBy which groups globally. Requires 'Key: equality.
• threadState is the streaming counterpart to mapFold—the results are lazy and the final state is not returned. This matches AsyncSeq's threadStateAsync.
• replicateInfiniteAsync takes unit -> #Task<'T> rather than a single Task<'T>, since Tasks are single-use.

Changes

File	Change
TaskSeqInternal.fs	11 new functions
TaskSeq.fs	Dispatch wrappers for all new functions
TaskSeq.fsi	XML-documented signatures
TaskSeq.*.Tests.fs	6 new test files, 326 new tests
release-notes.txt	Updated under 1.0.0

Test Status

✅ Build: dotnet build src/FSharp.Control.TaskSeq.sln -c Release — succeeded, 0 warnings, 0 errors
✅ Format: dotnet fantomas . --check — all files correctly formatted
✅ Tests: dotnet test ... -c Release — 4,942 passed, 2 skipped (infrastructure), 0 failed

Closes part of #345 (Group 1 complete, pending merge of #346 for distinctUntilChangedWith).

Generated by Repo Assist

• Fixes We want design parity with FSharp.Control.AsyncSeq #345

Generated by Repo Assist for issue #345 · ◷

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[dsyme]

/repo-assist We just merged a similar PR, if there's anythi

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🤖 This is an automated response from Repo Assist.

Confirmed — PR #350 was merged into main covering the same Group 1 AsyncSeq design-parity functions (replicateInfinite*, firstOrDefault, lastOrDefault, splitAt, zipWith*, chunkBy*, threadState*). This PR is correctly closed with no further action needed. Issue #345 has also been closed as completed.

Generated by Repo Assist for issue #349 · ◷

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