llm codec tests: F25 REHOME rows 108, 110, 350, 504, 505, 613, 614

[MattJackson]

What. These F25 coverage-map v2 REHOME rows have their home under busbar-plane-llm/src/codec/**. Each legacy crates/busbar-llm/src/engine/tests/* test is ported at equal strength: the same inputs, the same literal figures, and no circular check. The assertions run on the served codec path the row names.

row	legacy test	ported to
108	egress_dropped_controls_audit_tests.rs:89	bedrock/tests/tests.rs::openai_tool_choice_none_onto_bedrock_forwards_and_reports_the_drop: non-empty body, get_weather kept, toolChoice omitted, tool_choice=none in dropped controls
110	egress_dropped_controls_audit_tests.rs:245	anthropic/tests/ir_mapping_q57_tests.rs::native_structured_output_lane_drops_schema_less_json_and_reports_it
350	ingress_indistinguishability_tests.rs:2234	tests/proto/stream_translate_tests.rs::an_anthropic_tool_call_id_reaches_an_openai_client_remapped_and_unleaked: call_…, not toolu_origRAW123, raw id absent from the body, decodes back
504	mid_stream_error_tests.rs:294	tests/wire_shim_tests.rs::strip_router_shim_keys_removes_the_never_native_keys_per_egress
505	mid_stream_error_tests.rs:337	tests/wire_shim_tests.rs::shim_strip_then_rewrite_model_keeps_the_model_cross_protocol (plus the same-dialect relay byte check)
613	stop_sequence_cap_degrade_tests.rs:23	tests/proto/response_format_matrix_tests.rs::openai_to_cohere_over_cap_stop_sequences_are_clamped_not_rejected: six become [a..e]
614	stop_sequence_cap_degrade_tests.rs:63	…::openai_to_cohere_exactly_cap_stop_sequences_are_forwarded_whole

For rows 108 and 110, the legacy audit row (egress.control_unrepresentable) is fed by the dropped-control name, so the codec-level port pins that name. That is the "or dropped_egress_controls contains it" the row allows.

Rows 107 and 109 are in a separate PR stacked on #857, because #857 restores 1.5.5's response_format drop on Anthropic. Tests only; not $.

[MattJackson]

Rule 20 note from #1031 (row 155, draft): one disjoint hunk in stream_translate_tests.rs (synthesize_from_response takes the cap). A test merge is clean.