I've assigned @wpaulino as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

No issues found.

The change correctly fixes a real bug: fail_htlc_backwards_with_reason(payment_hash, ...) operates on claimable payments and is a no-op for intercepted HTLCs (which live in pending_intercepted_htlcs), so previously the queued HTLCs were never released and stayed held until expiry. Replacing it with fail_intercepted_htlc(htlc.intercept_id) is the correct API and is consistent with the existing pattern at service.rs:1050.

Verified:

• InterceptedHTLC.intercept_id exists and is the right identifier.
• Swallowing the result with let _ = is intentional and safe — in PendingChannelOpen state the only expected error is "not found" (already released), matching the PR description.
• The removed FailureCode import has no remaining uses in the file.
• No new lock-ordering/deadlock risk (peer_state → channel_manager ordering unchanged from the old code).
• The new test genuinely registers an intercept via the real payment flow and asserts it is released after channel_open_failed.

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Backported in #4683.