fix(combos): retry single targets only after cooldown

[luvs01]

Motivation

• A single-target combo retry path re-enabled the attempted target without confirming it had entered cooldown, allowing immediate duplicate dispatch for request-local refusals that intentionally record no cooldown.
• The change ensures that an exclusion-free same-target retry is attempted only when the failed target is actually cooling, preventing one-off resource amplification and preserving the intended semantics for request-local failures.

Description

• Require the failed target to be actively in cooldown before dropping the attempted-target exclusion in the single-target retry path by checking isComboTargetInCooldown in src/server/responses/core-combo.ts.
• Keep the existing advanceComboAfterFailure behavior for normal failover and only allow the exclusion-free pickWithWait when the target is cooled.
• Add an end-to-end regression test tests/server/server-combo-failover-e2e.test.ts that verifies a request-local incompatibility (Unsupported parameter: user / HTTP 400) is not retried when waitForCooldownMs is set.
• Changes touched: src/server/responses/core-combo.ts and tests/server/server-combo-failover-e2e.test.ts.

Testing

• Ran bun run typecheck which completed successfully.
• Ran the focused test suite with ./node_modules/.bin/bun test tests/server/server-combo-failover-e2e.test.ts and observed all relevant cases pass (focused run and the full file run both passed; the full file run reported 177 passed, 0 failed).
• Ran bun run structure:check which passed.
• Performed git diff --check with no issues reported; note that running bun test with an older system Bun (1.2.14) surfaced a tooling mismatch (node:zlib export) unrelated to this code change, while the repository-local Bun (v1.4.0) used for the focused test runs passed the suite.

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Codex Task

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-21T00:45:45.581775Z	4e22463	PR opened

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[github-actions]

✅ Deterministic PR hygiene checks passed.

[devin-ai-integration]

Fixed in 5d00b3a. comboFailureCooldownScope(...) is now computed once before advanceComboAfterFailure and kept; failedTargetCooled additionally requires failureCooldownScope !== "none", so a cooldown written by a concurrent request no longer arms the exclusion-free retry for a request-local refusal. Added a synchronized two-request regression test (a concurrent cooldown does not retry a request-local refusal) covering exactly this interleaving — verified to fail on the unfixed code.

[devin-ai-integration]

Fixed in 5d00b3a. The retry gate now preserves this failure's computed cooldown scope and requires both a cooldown-producing scope (!== "none") and an active target cooldown before dropping the attempted-target exclusion — a foreign cooldown written by a concurrent request can no longer replay this request's request-local rejection. Regression test added: a concurrent cooldown does not retry a request-local refusal.