* fix(model): surface backend startup exits
Preserve the local backend process exit code and bounded stderr diagnostic when the process dies before its gRPC service becomes ready.
Fixes#9050
Assisted-by: Codex:gpt-5
* fix(model): satisfy startup diagnostic checks
Assisted-by: Codex:gpt-5.6 [Codex]
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Co-authored-by: localai-org-maint-bot <306269227+localai-org-maint-bot@users.noreply.github.com>