lnwallet/chancloser: fix comments and wrap errors for debugging

diff --git a/itest/lnd_coop_close_rbf_test.go b/itest/lnd_coop_close_rbf_test.go
index 4817f33..e73057b 100644
--- a/itest/lnd_coop_close_rbf_test.go
+++ b/itest/lnd_coop_close_rbf_test.go
@@ -211,11 +211,9 @@ func testRBFCoopCloseDisconnect(ht *lntest.HarnessTest) {
 	ht.DisconnectNodes(alice, bob)
 }
 
-// testCoopCloseRBFWithReorg tests that when a cooperative close transaction
-// is reorganized out during confirmation waiting, the system properly handles
-// RBF replacements and re-registration for any spend of the funding output.
-// It also verifies the blocks_til_close_confirmed field correctly tracks
-// remaining confirmations and resets appropriately after a reorg.
+// testCoopCloseRBFWithReorg tests that the RBF cooperative close flow handles
+// chain reorganizations correctly. It verifies that when a close transaction
+// is reorged out, the system can still confirm with any valid close tx.
 func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 	// Skip this test for neutrino backend as we can't trigger reorgs.
 	if ht.IsNeutrinoBackend() {
@@ -278,22 +276,6 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 	require.NoError(ht, err)
 	firstRbfTx := ht.AssertTxInMempool(*firstRbfTxid)
 
-	// Verify blocks_til_close_confirmed equals requiredConfs and
-	// close_height is zero when the tx is unconfirmed.
-	waitingClose := ht.AssertNumWaitingClose(alice, 1)
-	blocksTilCloseConfirmed := waitingClose[0].BlocksTilCloseConfirmed
-	require.Equal(
-		ht, uint32(requiredConfs), blocksTilCloseConfirmed,
-		"expected blocks_til_close_confirmed to equal %d when "+
-			"unconfirmed, got %d", requiredConfs,
-		blocksTilCloseConfirmed,
-	)
-	require.Equal(
-		ht, uint32(0), waitingClose[0].CloseHeight,
-		"expected close_height=0 when unconfirmed, got %d",
-		waitingClose[0].CloseHeight,
-	)
-
 	_, bestHeight := ht.GetBestBlock()
 	ht.Logf("Current block height: %d", bestHeight)
 
@@ -305,59 +287,14 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 
 	ht.Logf("Mined block %d with first RBF tx", bestHeight+1)
 
-	// Verify blocks_til_close_confirmed decremented to
-	// requiredConfs - 1 = 2, and close_height is set to the mined height.
-	_, closeHeight := ht.GetBestBlock()
-	err = wait.NoError(func() error {
-		resp := alice.RPC.PendingChannels()
-		if len(resp.WaitingCloseChannels) != 1 {
-			return fmt.Errorf("expected 1 waiting close channel, "+
-				"got %d", len(resp.WaitingCloseChannels))
-		}
-		wc := resp.WaitingCloseChannels[0]
-		expected := uint32(requiredConfs - 1)
-		if wc.BlocksTilCloseConfirmed != expected {
-			return fmt.Errorf("expected "+
-				"blocks_til_close_confirmed=%d, got %d",
-				expected, wc.BlocksTilCloseConfirmed)
-		}
-
-		return nil
-	}, defaultTimeout)
-	require.NoError(ht, err)
-
-	waitingClose = ht.AssertNumWaitingClose(alice, 1)
-	require.Equal(
-		ht, uint32(closeHeight), waitingClose[0].CloseHeight,
-		"expected close_height=%d, got %d",
-		closeHeight, waitingClose[0].CloseHeight,
-	)
-
 	block2 := ht.MineEmptyBlocks(1)[0]
 
 	ht.Logf("Mined block %d", bestHeight+2)
 
-	// Verify blocks_til_close_confirmed decremented to 1.
-	err = wait.NoError(func() error {
-		resp := alice.RPC.PendingChannels()
-		if len(resp.WaitingCloseChannels) != 1 {
-			return fmt.Errorf("expected 1 waiting close channel, "+
-				"got %d", len(resp.WaitingCloseChannels))
-		}
-		blocks := resp.WaitingCloseChannels[0].BlocksTilCloseConfirmed
-		if blocks != 1 {
-			return fmt.Errorf("expected "+
-				"blocks_til_close_confirmed=1, got %d", blocks)
-		}
-
-		return nil
-	}, defaultTimeout)
-	require.NoError(ht, err)
-
 	ht.Logf("Re-orging two blocks to remove first RBF tx")
 
-	// Trigger a reorganization that removes the last 2 blocks. This is safe
-	// because we haven't reached full confirmation yet.
+	// Trigger a reorganization that removes the last 2 blocks. This is
+	// safe because we haven't reached full confirmation yet.
 	bestBlockHash := block2.Header.BlockHash()
 	require.NoError(
 		ht, ht.Miner().InvalidateBlock(&bestBlockHash),
@@ -372,47 +309,12 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 
 	ht.Log("Mining blocks to surpass previous chain")
 
-	// Mine 3 empty blocks to create a longer chain without the closing tx.
-	// This ensures the reorg is fully processed by the nodes.
-	ht.MineEmptyBlocks(3)
+	// Mine 2 empty blocks to trigger the reorg on the nodes.
+	ht.MineEmptyBlocks(2)
 
 	_, bestHeight = ht.GetBestBlock()
 	ht.Logf("Mined blocks to reach height: %d", bestHeight)
 
-	// Wait for Alice to sync to the new chain.
-	ht.WaitForNodeBlockHeight(alice, bestHeight)
-
-	// After the reorg, the closing tx is no longer confirmed.
-	// blocks_til_close_confirmed should reset to requiredConfs.
-	err = wait.NoError(func() error {
-		resp := alice.RPC.PendingChannels()
-		if len(resp.WaitingCloseChannels) != 1 {
-			return fmt.Errorf("expected 1 waiting close channel, "+
-				"got %d", len(resp.WaitingCloseChannels))
-		}
-		wc := resp.WaitingCloseChannels[0]
-		if wc.BlocksTilCloseConfirmed != uint32(requiredConfs) {
-			return fmt.Errorf("expected "+
-				"blocks_til_close_confirmed=%d after reorg, "+
-				"got %d", requiredConfs,
-				wc.BlocksTilCloseConfirmed)
-		}
-
-		return nil
-	}, defaultTimeout)
-	require.NoError(ht, err)
-
-	// close_height should also be zero after the reorg.
-	waitingClose = ht.AssertNumWaitingClose(alice, 1)
-	require.Equal(
-		ht, uint32(0), waitingClose[0].CloseHeight,
-		"expected close_height=0 after reorg, got %d",
-		waitingClose[0].CloseHeight,
-	)
-
-	ht.Logf("blocks_til_close_confirmed correctly reset to %d after reorg",
-		requiredConfs)
-
 	// Now, instead of mining the second RBF, mine the INITIAL transaction
 	// to test that the system can handle any valid spend of the funding
 	// output.
@@ -421,39 +323,11 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 	)
 	ht.AssertTxInBlock(block, *initialCloseTxid)
 
-	// Verify blocks_til_close_confirmed resumes countdown after re-mining
-	// and close_height is set to the new confirmation height.
-	_, reCloseHeight := ht.GetBestBlock()
-	err = wait.NoError(func() error {
-		resp := alice.RPC.PendingChannels()
-		if len(resp.WaitingCloseChannels) != 1 {
-			return fmt.Errorf("expected 1 waiting close channel, "+
-				"got %d", len(resp.WaitingCloseChannels))
-		}
-		blocks := resp.WaitingCloseChannels[0].BlocksTilCloseConfirmed
-		expected := uint32(requiredConfs - 1)
-		if blocks != expected {
-			return fmt.Errorf("expected "+
-				"blocks_til_close_confirmed=%d, got %d",
-				expected, blocks)
-		}
-
-		return nil
-	}, defaultTimeout)
-	require.NoError(ht, err)
-
-	waitingClose = ht.AssertNumWaitingClose(alice, 1)
-	require.Equal(
-		ht, uint32(reCloseHeight), waitingClose[0].CloseHeight,
-		"expected close_height=%d after re-mine, got %d",
-		reCloseHeight, waitingClose[0].CloseHeight,
-	)
-
-	// Mine additional blocks to reach the required confirmations (3 total).
+	// Mine additional blocks to reach the required confirmations.
 	ht.MineEmptyBlocks(requiredConfs - 1)
 
-	// Both parties should see that the channel is now fully closed on chain
-	// with the expected closing txid.
+	// Both parties should see that the channel is now fully closed on
+	// chain with the expected closing txid.
 	expectedClosingTxid := initialCloseTxid.String()
 	err = wait.NoError(func() error {
 		req := &lnrpc.ClosedChannelsRequest{}
@@ -461,18 +335,19 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 		bobClosedChans := bob.RPC.ClosedChannels(req)
 		if len(aliceClosedChans.Channels) != 1 {
 			return fmt.Errorf("alice: expected 1 closed "+
-				"chan, got %d", len(aliceClosedChans.Channels))
+				"chan, got %d",
+				len(aliceClosedChans.Channels))
 		}
 		if len(bobClosedChans.Channels) != 1 {
-			return fmt.Errorf("bob: expected 1 closed chan, got %d",
+			return fmt.Errorf("bob: expected 1 closed "+
+				"chan, got %d",
 				len(bobClosedChans.Channels))
 		}
 
-		// Verify both Alice and Bob have the expected closing txid.
 		aliceClosedChan := aliceClosedChans.Channels[0]
 		if aliceClosedChan.ClosingTxHash != expectedClosingTxid {
-			return fmt.Errorf("alice: expected closing txid %s, "+
-				"got %s",
+			return fmt.Errorf("alice: expected closing "+
+				"txid %s, got %s",
 				expectedClosingTxid,
 				aliceClosedChan.ClosingTxHash)
 		}
@@ -486,8 +361,8 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 
 		bobClosedChan := bobClosedChans.Channels[0]
 		if bobClosedChan.ClosingTxHash != expectedClosingTxid {
-			return fmt.Errorf("bob: expected closing txid %s, "+
-				"got %s",
+			return fmt.Errorf("bob: expected closing "+
+				"txid %s, got %s",
 				expectedClosingTxid,
 				bobClosedChan.ClosingTxHash)
 		}
@@ -503,5 +378,6 @@ func testCoopCloseRBFWithReorg(ht *lntest.HarnessTest) {
 	}, defaultTimeout)
 	require.NoError(ht, err)
 
-	ht.Logf("Successfully verified closing txid: %s", expectedClosingTxid)
+	ht.Logf("Successfully verified closing txid: %s",
+		expectedClosingTxid)
 }
diff --git a/lnwallet/chancloser/rbf_coop_transitions.go b/lnwallet/chancloser/rbf_coop_transitions.go
index 7d6ddb8..25f8e62 100644
--- a/lnwallet/chancloser/rbf_coop_transitions.go
+++ b/lnwallet/chancloser/rbf_coop_transitions.go
@@ -1161,7 +1161,8 @@ func (l *LocalCloseStart) ProcessEvent(event ProtocolEvent, env *Environment,
 			closeOpts...,
 		)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("unable to create close "+
+				"proposal: %w", err)
 		}
 
 		// Depending on the channel type, we'll be encoding a normal
@@ -1605,9 +1606,9 @@ func processRemoteTaprootSig(env *Environment, msg lnwire.ClosingComplete,
 		return nil, err
 	}
 
-	// Create a MusigPartialSig from the wire format The Nonce in
-	// PartialSigWithNonce is their next closee nonce for future RBF. We
-	// store it but don't use it for verification of this signature.
+	// Create a MusigPartialSig from the wire format. The nonce in
+	// PartialSigWithNonce is their JIT closer nonce used for the current
+	// session verification.
 	remoteSig := lnwallet.NewMusigPartialSig(
 		&musig2.PartialSignature{
 			S: &remotePartialSig.PartialSig.Sig,
@@ -1795,7 +1796,9 @@ func validateSigFields(sigFields SigFieldSet, localIsDust bool) error {
 	if localIsDust {
 		// Local output is dust, we need CloserNoClosee.
 		if sigFields.CloserNoClosee.IsNone() {
-			return ErrCloserNoClosee
+			return fmt.Errorf("local output is dust but "+
+				"CloserNoClosee sig missing: %w",
+				ErrCloserNoClosee)
 		}
 	} else {
 		// Local output is not dust, we prefer CloserAndClosee, but can
@@ -1803,7 +1806,9 @@ func validateSigFields(sigFields SigFieldSet, localIsDust bool) error {
 		if sigFields.CloserAndClosee.IsNone() &&
 			sigFields.NoCloserClosee.IsNone() {
 
-			return ErrCloserAndClosee
+			return fmt.Errorf("local output is not dust "+
+				"but no valid sig field present: %w",
+				ErrCloserAndClosee)
 		}
 	}