Standalone console smoke browser ownership controls

At clean90718f10af9f33577b8876ca7521cf007b86c51b, the routine source command ran18 tests, zero failures/skips, exit0. Four new controls cover held-FD borrowing and release after constructor refusal, body failure cleanup and refusal of unconfirmed stop; unchanged bridge/runtime controls remain included. This is synthetic ownership evidence, not a live browser or candidate smoke.

python3 -B /run/media/kmosoti/data/FabricO11y/results/candidate-build-fresh-8fb6f413179b-01/run-step-console-smoke-ownership-01.py console-smoke-ownership-source-01 1073741824 env PYTHONPATH=tools/qualification:tools:tools/ui:tools/bench/labs/completion python3 -B -m unittest -v test_console_bridge_smoke test_console_bridge test_release_runtime

Actual21:06:36.545560–21:06:37.551948UTC, source clean before/after. Strict namespace census62,937,764,386bytes plus1GiB reserved; DATA only,16/20GiB/noSwap1800seconds. Outer stop confirmed and temporary scratch removed. Resource receipt SHA2569c88e64e3ee4ef964ceee5cdd876d8c0a3032406905bae34a2a20166f370b59d; log SHA256e64611a88269c469db44804e2e2648798036b04f4ae670c1fa3bc5d1745cf1fd. Actual peak35926016bytes, no OOM events.

The caller delegates before any server child, creates the existing1GiB/850MiB browser budget, passes its held exclusive identity and finite deadline to the existing supervisor, and bounds close to20seconds. Its prior4GB combined fixture cap remains; registered pressure/outage6/8GiB envelopes are unchanged. Failed scratch survives rather than being unconditionally deleted. The helper's private browser wait domain is unchanged.

Ordinary merge into the combined acceptance runtime preserves both branches. Required combined new-product-graph checks and actual replacement-candidate standalone smoke remain pending; historical package results supply no credit.