57f6762ca0
Move the five stream-drop diagnostic helpers + the headers tuple: * STREAM_DIAG_HEADERS — cf-ray, x-openrouter-provider, x-request-id, etc. * stream_diag_init — fresh per-attempt diagnostic dict * stream_diag_capture_response — snapshot upstream headers + HTTP status * flatten_exception_chain — compact Outer(msg) <- Inner(msg) rendering * log_stream_retry — structured WARNING with provider/bytes/elapsed/ttfb * emit_stream_drop — user-facing status line + activity touch AIAgent keeps thin forwarder methods (and exposes the headers tuple as _STREAM_DIAG_HEADERS for back-compat). All test patches and call sites unchanged. tests/run_agent/ + tests/agent/: 4313 passed (same pre-existing test_auxiliary_client failure). run_agent.py: 13470 -> 13227 lines (-243).