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>

include/ui/chat/cast_sequence_tracker.hpp

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <unordered_map>
+
+namespace wowee {
+namespace ui {
+
+/**
+ * /castsequence persistent state — shared across all macros using the same spell list.
+ *
+ * Extracted from chat_panel_commands.cpp static global (Phase 1.5 of chat_panel_ref.md).
+ * Keyed by the normalized (lowercase, comma-joined) spell sequence string.
+ */
+class CastSequenceTracker {
+public:
+    struct State {
+        size_t   index          = 0;
+        float    lastPressSec   = 0.0f;
+        uint64_t lastTargetGuid = 0;
+        bool     lastInCombat   = false;
+    };
+
+    /** Get (or create) the state for a given sequence key. */
+    State& get(const std::string& seqKey) { return states_[seqKey]; }
+
+    /** Reset all tracked sequences. */
+    void clear() { states_.clear(); }
+
+private:
+    std::unordered_map<std::string, State> states_;
+};
+
+} // namespace ui
+} // namespace wowee