* fix(providers): report provider-selection diagnostics when the selected provider refuses its profile
An explicitly selected provider that refuses the target during profile resolution now yields the target_unsupported selection error with its candidates and rejections, keeping the refusal's message and, when present, its specific recovery.
Fixes#3930
* fix(providers): keep refusal evidence and cleanup ownership on selection failures
A refusal with unconfirmed cleanup is returned unchanged; otherwise the selection failure carries the refusal's captured output, diagnostics, partial observation and cause. Registry tests cover the copied recovery and the cleanup guard.