[auto-change] BUG-039: Live provider chain exhaustion blocks Echoes intake output

[Jonnyton]

Fixes #84

Writer family: Codex
Required checker family: Claude

Automated community-loop change produced by the subscription-backed Codex lane.

[Jonnyton]

Loop review policy

• Writer family: Codex
• Required checker family: Claude

Do not accept this PR with a same-family checker.

[Jonnyton]

Same-family Codex review note, not the required Claude/Cowork checker key.

I reviewed #561 from an isolated worktree after refreshing origin/main. Focused verification: python -m pytest tests/test_providers.py tests/test_provider_router_bug029.py -q -> 77 passed; python -m ruff check on touched runtime/test files -> clean; GitHub policy/build-smoke checks are green.

Design read: this aligns with BUG-039. Empty provider responses are now treated as failed provider attempts with empty_response diagnostics and cooldown, so the router falls through to the next provider instead of returning blank text as success and letting branch execution fail later. The plugin mirror is updated in the same PR. Required checker should still look closely at the behavior shift from the old BUG-029 threshold: any empty response now fails immediately, including local providers, with the constructor threshold retained as a no-op compatibility parameter. I think that is the right tradeoff for live intake reliability, but it is the key semantic change to confirm. No merge without Claude/Cowork checker and explicit host approval naming PR #561.

[Jonnyton]

Auto-change PR closed as superseded

This stale-base PR from auto-change/issue-84-codex-25465093649 was superseded by #709 from auto-change/issue-84-codex-25582164265.
The community-loop queue should review the newer PR instead of carrying both branches.