[client] Preserve partition keys in typed deletes

[fxbing]

Purpose

Closes #4303

Fix typed deletes on partitioned primary-key tables failing with Partition value shouldn't be null. despite the POJO containing the partition values.

Brief change log

• Use logical primary keys for the delete projection and full-row expansion in TypedUpsertWriterImpl.
• Add regression coverage through the real writer delegation path, capturing WriterClient.send to verify partitioned and nonpartitioned target paths with a null payload.

Tests

• Confirmed the partitioned regression fails on the old code and both new tests pass after the fix.
• All 51 focused and adjacent tests passed under Java 11; Spotless and Checkstyle passed.
• Tests reused locally installed sibling SNAPSHOT artifacts. No full reactor rebuild or server-side deletion E2E was run.

API and Format

No public API, wire-protocol, or storage-format changes.

Generative AI disclosure

AI-assisted implementation and review using Claude Code and OpenAI Codex.