debug: add GO interaction diagnostics at every decision point

Adds [GO-DIAG] WARNING-level logs at:
- Right-click dispatch (raypick hit / re-interact with target)
- interactWithGameObject entry + all BLOCKED paths
- SMSG_SPELL_GO (wasInTimedCast, lastGoGuid, pendingGoGuid state)
- SMSG_LOOT_RESPONSE (items, gold, guid)
- Raypick candidate GO positions (entity pos + hit center + radius)

These logs will pinpoint exactly where the interaction fails:
- No GO-DIAG lines = GOs not in entity manager / not visible
- Raypick GO pos=(0,0,0) = GO position not set from update block
- BLOCKED = guard condition preventing interaction
- SPELL_GO wasInTimedCast=false = timer race (already fixed)

src/game/spell_handler.cpp

@@ -948,6 +948,12 @@ void SpellHandler::handleSpellGo(network::Packet& packet) {
 
         const bool wasInTimedCast = casting_ && (data.spellId == currentCastSpellId_);
 
+        LOG_WARNING("[GO-DIAG] SPELL_GO: spellId=", data.spellId,
+                    " casting=", casting_, " currentCast=", currentCastSpellId_,
+                    " wasInTimedCast=", wasInTimedCast,
+                    " lastGoGuid=0x", std::hex, owner_.lastInteractedGoGuid_,
+                    " pendingGoGuid=0x", owner_.pendingGameObjectInteractGuid_, std::dec);
+
         casting_ = false;
         castIsChannel_ = false;
         currentCastSpellId_ = 0;
@@ -955,6 +961,8 @@ void SpellHandler::handleSpellGo(network::Packet& packet) {
 
         // Gather node looting: re-send CMSG_LOOT now that the cast completed.
         if (wasInTimedCast && owner_.lastInteractedGoGuid_ != 0) {
+            LOG_WARNING("[GO-DIAG] Sending CMSG_LOOT for GO 0x", std::hex,
+                        owner_.lastInteractedGoGuid_, std::dec);
             owner_.lootTarget(owner_.lastInteractedGoGuid_);
             owner_.lastInteractedGoGuid_ = 0;
         }