Channel stuck in CLOSINGD_COMPLETE if funding never confirms

[ksedgwic]

When a mutual close negotiation completes on a channel whose funding
tx never confirmed, the channel state is stuck. The signed close tx
is permanently invalid — its input is a 2-of-2 funding output that
does not exist on chain — so the state machine has no path from
CLOSINGD_COMPLETE to FUNDING_SPEND_SEEN / ONCHAIN. The channel
sits indefinitely with no cleanup.

Concrete instances

More details about the following channels can be found in clboss
issue #312. @ksedgwic
operates one node; the issue reporter operates the other.

Channel A

• channel_id: 98f1632d48f0d94d86161a8b4745a97d34c72beb3a6f1db4050210d18aae1e6e
• funding_txid: 6f1eae8ad1100205b41d6f3aeb2bc7347da945478b1a16864dd9f0482d63f198 — never confirmed on chain
• close tx (signed, in DB on both sides): 92ce9629985b686b1b9b433b78561fe33d188c71c1131d100798bb24354fe57d — never broadcast; 404 on every explorer
• opener: counterparty; closer: us
• created 2026-01-31; reached CLOSINGD_COMPLETE 2026-02-24
• still in CLOSINGD_COMPLETE on both sides as of 2026-04-30

Channel B

• channel_id: 264d24bdade7908c31e4d8338368d321c08f4b50fbaf92761da239302ac2cf45
• funding_txid: 45cfc22a3039a21d7692affb504b8fc021d3688333d8e4318c90e7adbd244d26 — never confirmed
• close tx (signed, in DB on both sides): d00300b5acb9b7105d2e11d176a1bee5cf05db8e38b6edc6cd8224ff226665f8 — never broadcast
• opener: counterparty; closer: us
• created 2026-02-28; reached CLOSINGD_COMPLETE 2026-03-11
• still in CLOSINGD_COMPLETE on both sides as of 2026-04-30

Reproducer

#9103