test: derive DKG lookahead from RPC default in feature_llmq_evo

Address CodeRabbit feedback on the dkginfo test: name the previously
hardcoded values and document their C++ sources (llmq_test_platform
dkgInterval in src/llmq/params.h, WORK_DIFF_DEPTH in src/llmq/snapshot.h),
and drop the explicit lookahead argument since 'quorum dkginfo' already
defaults lookahead_blocks to llmq::WORK_DIFF_DEPTH.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: thepastaclaw

test/functional/feature_llmq_evo.py

@@ -86,18 +86,24 @@ def run_test(self):
 
         self.log.info("Test 'quorum dkginfo' upcoming platform DKG participation uses only EvoNodes")
         nodes = [self.nodes[0]] + [mn.get_node(self) for mn in self.mninfo]
+        # Mirrors llmq_test_platform.dkgInterval (src/llmq/params.h) and
+        # llmq::WORK_DIFF_DEPTH (src/llmq/snapshot.h): the quorum work block is
+        # mined work_diff_depth blocks before the quorum height, so mine up to
+        # that point to make the upcoming DKG predictable.
         dkg_interval = 24
+        work_diff_depth = 8
         tip = self.nodes[0].getblockcount()
         blocks_to_next_dkg = dkg_interval - (tip % dkg_interval)
-        blocks_to_mine = blocks_to_next_dkg - 8
+        blocks_to_mine = blocks_to_next_dkg - work_diff_depth
         if blocks_to_mine > 0:
             self.generate(self.nodes[0], blocks_to_mine, sync_fun=lambda: self.sync_blocks(nodes))
 
         tip = self.nodes[0].getblockcount()
         expected_quorum_height = tip - (tip % dkg_interval) + dkg_interval
         predicted_members = {}
         for mn in self.mninfo:
-            dkg_info = mn.get_node(self).quorum("dkginfo", mn.proTxHash, 8)
+            # lookahead_blocks defaults to llmq::WORK_DIFF_DEPTH, exactly covering the upcoming DKG
+            dkg_info = mn.get_node(self).quorum("dkginfo", mn.proTxHash)
             upcoming_platform = [d for d in dkg_info["upcoming_dkgs"] if d["llmqType"] == 106]
             assert_equal(len(upcoming_platform), 1)
             predicted_platform = upcoming_platform[0]