Draft: Fix #2155 - Streaming gzipped responses

[ReadingNought]

Summary

Enable automatic content decoding on Response.raw so streamed gzip-encoded responses can be consumed directly via file-like readers.

Root Cause

Requests built responses with raw.decode_content=False, so consumers reading from response.raw got compressed bytes by default. This breaks file-like streaming parsers that call .read() and expect decoded content.

Changes Made

• Set response.raw.decode_content = True in HTTPAdapter.build_response.
• Added a regression test in tests/test_adapters.py to verify build_response enables decoded raw reads by default.

Verification

• Ran: PYTHONPATH=src pytest -q tests/test_adapters.py
• Result: 2 passed

Notes

• Explicit reads that need wire-level compressed bytes can still request decode_content=False on read/stream calls.

Closes #2155