Phase 1, Task 3: Convert decompress_and_process to chunk-based processing

[aram356]

Parent: #563
Phase: #566

Summary

decompress_and_process() calls read_to_end() to decompress the entire body into memory. Used by process_gzip_to_none, process_deflate_to_none, process_brotli_to_none. Convert to chunk-based read loop matching process_uncompressed.

Changes

• Replace read_to_end() with chunk read loop (read → process_chunk() → write_all() → repeat)
• Follow the process_uncompressed pattern as reference
• Add gzip-to-none correctness test
• Callers (*_to_none functions) unchanged — same signature

File: crates/trusted-server-core/src/streaming_processor.rs:227-262

Plan

See docs/superpowers/plans/2026-03-25-streaming-response.md — Task 3