Fix buff bar: opcode merge, isBuff flag, and duration countdown

Root cause: OpcodeTable::loadFromJson() cleared all mappings before
loading the expansion JSON, so any WotLK opcode absent from Turtle WoW's
opcodes.json (including SMSG_AURA_UPDATE and SMSG_AURA_UPDATE_ALL) was
permanently lost. Changed loadFromJson to patch/merge on top of existing
defaults so only explicitly listed opcodes are overridden.

Also fix isBuff border color: was testing flag 0x02 (effect 2 active)
instead of 0x80 (negative/debuff flag).

Add client-side duration countdown: AuraSlot.receivedAtMs is stamped
when the packet arrives; getRemainingMs(nowMs) subtracts elapsed time so
buff tooltips show accurate remaining duration instead of stale snapshot.

src/game/game_handler.cpp

@@ -7162,7 +7162,14 @@ void GameHandler::handleAuraUpdate(network::Packet& packet, bool isAll) {
         if (isAll) {
             auraList->clear();
         }
-        for (const auto& [slot, aura] : data.updates) {
+        uint64_t nowMs = static_cast<uint64_t>(
+            std::chrono::duration_cast<std::chrono::milliseconds>(
+                std::chrono::steady_clock::now().time_since_epoch()).count());
+        for (auto [slot, aura] : data.updates) {
+            // Stamp client timestamp so the UI can count down duration locally
+            if (aura.durationMs >= 0) {
+                aura.receivedAtMs = nowMs;
+            }
             // Ensure vector is large enough
             while (auraList->size() <= slot) {
                 auraList->push_back(AuraSlot{});

src/game/opcode_table.cpp

@@ -698,13 +698,12 @@ bool OpcodeTable::loadFromJson(const std::string& path) {
 
     std::string json((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
 
-    // Save old tables so we can restore on failure
+    // Merge/patch on top of existing table (WotLK defaults must be loaded first).
+    // Opcodes NOT in the JSON keep their current mapping, so expansion-specific
+    // JSONs only need to list entries that differ from the WotLK baseline.
     auto savedLogicalToWire = logicalToWire_;
     auto savedWireToLogical = wireToLogical_;
 
-    logicalToWire_.clear();
-    wireToLogical_.clear();
-
     // Parse simple JSON: { "NAME": "0xHEX", ... } or { "NAME": 123, ... }
     size_t pos = 0;
     size_t loaded = 0;
@@ -746,6 +745,11 @@ bool OpcodeTable::loadFromJson(const std::string& path) {
         auto logOp = nameToLogical(key);
         if (logOp) {
             uint16_t logIdx = static_cast<uint16_t>(*logOp);
+            // Remove stale reverse-mapping for this logical opcode's old wire value
+            auto oldIt = logicalToWire_.find(logIdx);
+            if (oldIt != logicalToWire_.end()) {
+                wireToLogical_.erase(oldIt->second);
+            }
             logicalToWire_[logIdx] = wire;
             wireToLogical_[wire] = logIdx;
             ++loaded;

src/ui/game_screen.cpp

@@ -4044,7 +4044,7 @@ void GameScreen::renderBuffBar(game::GameHandler& gameHandler) {
 
             ImGui::PushID(static_cast<int>(i));
 
-            bool isBuff = (aura.flags & 0x02) != 0;
+            bool isBuff = (aura.flags & 0x80) == 0;  // 0x80 = negative/debuff flag
             ImVec4 borderColor = isBuff ? ImVec4(0.2f, 0.8f, 0.2f, 0.9f) : ImVec4(0.8f, 0.2f, 0.2f, 0.9f);
 
             // Try to get spell icon
@@ -4078,12 +4078,16 @@ void GameScreen::renderBuffBar(game::GameHandler& gameHandler) {
                 }
             }
 
-            // Tooltip with spell name and duration
+            // Tooltip with spell name and live countdown
             if (ImGui::IsItemHovered()) {
                 std::string name = spellbookScreen.lookupSpellName(aura.spellId, assetMgr);
                 if (name.empty()) name = "Spell #" + std::to_string(aura.spellId);
-                if (aura.durationMs > 0) {
-                    int seconds = aura.durationMs / 1000;
+                uint64_t nowMs = static_cast<uint64_t>(
+                    std::chrono::duration_cast<std::chrono::milliseconds>(
+                        std::chrono::steady_clock::now().time_since_epoch()).count());
+                int32_t remaining = aura.getRemainingMs(nowMs);
+                if (remaining > 0) {
+                    int seconds = remaining / 1000;
                     if (seconds < 60) {
                         ImGui::SetTooltip("%s (%ds)", name.c_str(), seconds);
                     } else {