fix(sync): prioritize getblockchaininfo and pause chat scans while behind

The node kept falling behind the network near the tip because sync
DETECTION was starved: getblockchaininfo was queued behind the
O(mapWallet) wallet RPCs (z_gettotalbalance / z_listunspent), so
longestchain went stale, the wallet decided it was "synced", and it
resumed hammering cs_main — a feedback loop.

- Issue getblockchaininfo FIRST each cycle and skip the balance/address/
  tx refresh entirely while behind, so sync state (and kSyncProfile)
  updates before any heavy wallet scan runs.
- Gate the two chat note scans (refreshChatNoteBudgetNode /
  fastScanChatMemos) on effectivelySyncing() and the active page, so chat
  memo scanning no longer competes with block connection during sync.
- Windows debug.log tailer: reset the read offset when dragonxd truncates
  the log on startup (it was stranding at Block:0 with no witness/rescan
  progress).
- Tests cover the getblockchaininfo-first ordering and behind-skip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/daemon/embedded_daemon.cpp

@@ -816,11 +816,21 @@ void EmbeddedDaemon::drainOutput()
     }
     
     size_t currentSize = static_cast<size_t>(fileSize.QuadPart);
+    // Truncation / rotation detection. dragonxd shrinks debug.log on startup (ShrinkDebugFile keeps
+    // only the tail once it has grown large), so the file can become SMALLER than where we left off.
+    // Our offset was set to the PRE-shrink size at spawn, so without this reset it stays stranded ahead
+    // of the freshly-truncated file and we read NOTHING for the whole session — no block height (status
+    // bar shows "Block: 0") and, worse, no witness-rebuild progress, since the "Setting Initial Sapling
+    // Witness …" lines the warmup progress bar parses only exist in debug.log on Windows. On a shrink,
+    // restart from the new beginning; the parser is monotonic and converges as it reaches current output.
+    if (currentSize < debug_log_offset_) {
+        debug_log_offset_ = 0;
+    }
     if (currentSize <= debug_log_offset_) {
         CloseHandle(hFile);
         return;  // No new data
     }
-    
+
     // Seek to where we left off
     LARGE_INTEGER seekPos;
     seekPos.QuadPart = static_cast<LONGLONG>(debug_log_offset_);