[Repo Assist] perf: reuse ResizeArray buffer in chunkBy and chunkByAsync

[github-actions]

🤖 This is an automated pull request from Repo Assist.

Summary

TaskSeq.chunkBy and TaskSeq.chunkByAsync previously allocated a fresh ResizeArray<'T> at every chunk boundary:

yield prevKey, currentChunk.ToArray()
currentChunk <- ResizeArray<'T>()   // allocates every time
currentChunk.Add item

Since ToArray() already creates an independent copy of the chunk contents, the existing ResizeArray backing array can be safely reused by calling Clear() instead:

yield prevKey, currentChunk.ToArray()
currentChunk.Clear()                // zero cost — no heap allocation
currentChunk.Add item

Root Cause

ResizeArray<'T>() allocates a new object on the heap (with default initial capacity 4). Clear() simply sets the internal count to zero and retains the existing backing array. Because ToArray() captures a snapshot before the clear, the yielded arrays are unaffected.

Impact

• Eliminates one ResizeArray allocation per chunk boundary
• Reduces GC pressure proportionally to the number of distinct key transitions in the source sequence
• Particularly noticeable for sequences with many short runs (e.g., alternating keys)

Test Status

• ✅ Build: dotnet build — succeeded, 0 warnings
• ✅ Tests: dotnet test — 5017 passed, 2 skipped (skipped tests are pre-existing infrastructure-only skips)
• ✅ Formatting: dotnet fantomas . --check — no issues

Generated by 🌈 Repo Assist at {run-started}. Learn more.

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@1f672aef974f4246124860fc532f82fe8a93a57e