Fix mempool.get_info, testmempoolaccept and outpoint.subscribe with the Palladium daemon

- mempool.get_info: the daemon has no incrementalrelayfee in getmempoolinfo,
  read incrementalfee from getnetworkinfo
- testmempoolaccept: the daemon does not report wtxid
- outpoint.subscribe: refuse the subscription (Coin.DAEMON_HAS_TXO_SPENDER_INDEX)
  instead of closing the session at the next block, when the daemon errors

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/server/test_daemon.py

@@ -261,6 +261,17 @@ async def test_mempool_info(daemon):
     assert await daemon.mempool_info() == expected_result
 
 
+@pytest.mark.asyncio
+async def test_mempool_info_incrementalfee_from_networkinfo(daemon):
+    # Palladium Core: getmempoolinfo has no 'incrementalrelayfee', getnetworkinfo has 'incrementalfee'
+    daemon.session = ClientSessionGood(
+        ('getmempoolinfo', [], {'mempoolminfee': 0.00001, 'minrelaytxfee': 0.00002, 'other': 'cruft'}),
+        ('getnetworkinfo', [], {'incrementalfee': 0.00003, 'other': 'cruft'}),
+    )
+    assert await daemon.mempool_info() == {
+        'mempoolminfee': 0.00001, 'minrelaytxfee': 0.00002, 'incrementalrelayfee': 0.00003}
+
+
 @pytest.mark.asyncio
 async def test_mempool_txids_hum(daemon):
     hashes = ['hex_hash1', 'hex_hash2']