[iremyux]

This is the ZIP counterpart to #129282, which deduplicated the sync/async implementations of TarReader/TarWriter using the IReadWriteAdapter pattern. This PR applies the same approach to System.IO.Compression's ZIP implementation, merging each sync/async method pair.

Fixes #127380

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[Copilot]

🟡 Changes recommended

Encrypted Update-mode operations regress password-error recovery and write-only replacement when the original AES salt is unavailable.

2 open findings

• Failed password leaves Update entry stuck, blocking retry · New
• Write-only replacement fails when AES salt is unavailable · New

What changed in this PR

Applies the TAR adapter pattern from #129282 to ZIP, sharing synchronous and asynchronous implementations to address #127380.

Changes:

• Introduces shared adapter-based archive, entry, and ZIP block operations.
• Removes duplicated async implementations.
• Updates project references to include ReadWriteAdapter.

Builds and tests were not run.

File	Description
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipHelper.cs	Shares signature-search logic.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipHelper.Async.cs	Removes duplicate async helpers.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipBlocks.cs	Shares ZIP block reading and writing.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipBlocks.Async.cs	Removes duplicate async block operations.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipArchiveEntry.cs	Consolidates entry operations and stream lifecycle handling.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipArchiveEntry.Async.cs	Removes separate async entry implementation.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipArchive.cs	Shares directory parsing and archive finalization.
src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipArchive.Async.cs	Retains async entry points; removes duplicated internals.
src/​libraries/​System.IO.Compression/​src/​System.IO.Compression.csproj	Includes the adapter and removes deleted sources.

🧠 Review effort: Balanced

[Copilot]

🔵 Needs a closer look

Cancellation during encrypted-header reading leaves the entry marked open for writing, blocking retries.

0 open findings

2 resolved since last review

• Write-only replacement fails when AES salt is unavailable
• Failed password leaves Update entry stuck, blocking retry

Previously missed (1)

In code that hasn't changed since last review

Cancellation during encrypted header read blocks Update-mode retry

src/​libraries/​System.IO.Compression/​src/​System/​IO/​Compression/​ZipArchiveEntry.cs:879

In Update mode, cancellation while the AES or ZipCrypto factory reads the encryption header now leaves _currentlyOpenForWrite set and _storedUncompressedData allocated. OperationCanceledException bypasses this cleanup, so retrying with a fresh token throws UpdateModeOneStream. Previously, the encrypted async path acquired the decryption stream before setting this state. Run this rollback for all acquisition/copy failures and rethrow the original exception. Add a regression test that cancels during the encryption-header read and then successfully retries.

🧠 Review effort: Balanced