refactor(chat): decompose into modular architecture, add GM commands, fix protocol

- Extract ChatPanel monolith into 15+ focused modules under ui/chat/
  (ChatInput, ChatTabManager, ChatTabCompleter, ChatMarkupParser,
  ChatMarkupRenderer, ChatCommandRegistry, ChatBubbleManager,
  ChatSettings, MacroEvaluator, GameStateAdapter, InputModifierAdapter)
- Split 2700-line chat_panel_commands.cpp into 11 command modules
- Add GM command handling: 190-command data table, dot-prefix interception,
  tab-completion, /gmhelp with category filter
- Fix ChatType enum to match WoW wire protocol (SAY=0x01 not 0x00);
  values 0x00-0x1B shared across Vanilla/TBC/WotLK
- Fix BG_SYSTEM_* values from 82-84 (UB in bitmask shifts) to 0x24-0x26
- Fix infinite Enter key loop after teleport (disable TOGGLE_CHAT repeat,
  add 2-frame input cooldown)
- Add tests: chat_markup_parser, chat_tab_completer, gm_commands,
  macro_evaluator

Signed-off-by: Pavel Okhlopkov <pavel.okhlopkov@flant.com>

src/ui/chat/chat_input.cpp

@@ -0,0 +1,68 @@
+#include "ui/chat/chat_input.hpp"
+
+namespace wowee { namespace ui {
+
+// Push a message to sent-history (skip pure whitespace, cap at kMaxHistory).
+void ChatInput::pushToHistory(const std::string& msg) {
+    bool allSpace = true;
+    for (char c : msg) {
+        if (!std::isspace(static_cast<unsigned char>(c))) { allSpace = false; break; }
+    }
+    if (allSpace) return;
+
+    // Remove duplicate of last entry if identical
+    if (sentHistory_.empty() || sentHistory_.back() != msg) {
+        sentHistory_.push_back(msg);
+        if (static_cast<int>(sentHistory_.size()) > kMaxHistory)
+            sentHistory_.erase(sentHistory_.begin());
+    }
+    historyIdx_ = -1;  // reset browsing position after send
+}
+
+// Navigate up through sent-history. Returns the entry or "" if at start.
+std::string ChatInput::historyUp() {
+    const int histSize = static_cast<int>(sentHistory_.size());
+    if (histSize == 0) return "";
+
+    if (historyIdx_ == -1)
+        historyIdx_ = histSize - 1;
+    else if (historyIdx_ > 0)
+        --historyIdx_;
+
+    return sentHistory_[historyIdx_];
+}
+
+// Navigate down through sent-history. Returns the entry or "" if past end.
+std::string ChatInput::historyDown() {
+    const int histSize = static_cast<int>(sentHistory_.size());
+    if (histSize == 0 || historyIdx_ == -1) return "";
+
+    ++historyIdx_;
+    if (historyIdx_ >= histSize) {
+        historyIdx_ = -1;
+        return "";
+    }
+    return sentHistory_[historyIdx_];
+}
+
+// Insert a spell / item link into the chat input buffer (shift-click).
+void ChatInput::insertLink(const std::string& link) {
+    if (link.empty()) return;
+    size_t curLen = std::strlen(buffer_);
+    if (curLen + link.size() + 1 < sizeof(buffer_)) {
+        strncat(buffer_, link.c_str(), sizeof(buffer_) - curLen - 1);
+        moveCursorToEnd_ = true;
+        focusRequested_  = true;
+    }
+}
+
+// Activate the input field with a leading '/' (slash key).
+void ChatInput::activateSlashInput() {
+    focusRequested_ = true;
+    buffer_[0] = '/';
+    buffer_[1] = '\0';
+    moveCursorToEnd_ = true;
+}
+
+} // namespace ui
+} // namespace wowee