fix(cli): preserve pack full encoding on push

[peters]

Summary

• Preserve full_compression_level and full_zstd_workers when surge push replaces a release index entry already written by surge pack.
• Only reuse the recorded encoding when the existing entry's full filename, size, and SHA-256 match the package being pushed.
• Add a regression test for the full-only/checkpoint release path where push previously erased pack metadata.
• Include mechanical lint cleanup required by the current clippy toolchain.

Root Cause

PR #90 made pack record full-archive encoding and made promote refuse to guess when encoding is unknown. The missed path was surge push: after pack wrote the correct metadata, push rebuilt the same release entry and reset the encoding fields to the unrecorded sentinels. Full-only releases then had neither recorded fields nor a primary delta to infer from, so later channel promotion could not build a byte-identical channel delta.

Validation

• ./scripts/sync-surge-core-vendor.sh --check
• ./scripts/check-version-sync.sh
• cargo fmt --all -- --check
• RUSTFLAGS="-D warnings" cargo test --workspace
• cargo clippy --all-targets --all-features -- -D warnings
• cargo clippy --workspace --lib --bins --examples -- -D warnings -D clippy::unwrap_used -D clippy::expect_used
• cargo clippy --workspace --all-targets --all-features -- -D warnings -W clippy::pedantic
• dotnet format dotnet/Surge.slnx --verify-no-changes
• dotnet test dotnet/Surge.slnx --configuration Release

[peters]

Closing as superseded by #102. Current main preserves full-package encoding through the pack-generated metadata sidecar, which push validates and records on the first upload path. The remaining change here only preserves encoding when re-pushing an already-indexed identical full artifact without that sidecar, so it is not needed for the original promotion metadata issue.