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/chat_markup_parser.hpp

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <imgui.h>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace wowee {
+namespace ui {
+
+/**
+ * Segment types produced by ChatMarkupParser.
+ *
+ * Each segment represents a contiguous piece of a chat message
+ * after WoW markup (|c...|r, |Hitem:...|h[...]|h, URLs) has been decoded.
+ */
+enum class SegmentType {
+    Text,               // Plain text (render with base message color)
+    ColoredText,        // Text with explicit |cAARRGGBB color
+    ItemLink,           // |Hitem:ID:...|h[Name]|h
+    SpellLink,          // |Hspell:ID:...|h[Name]|h
+    QuestLink,          // |Hquest:ID:LEVEL|h[Name]|h
+    AchievementLink,    // |Hachievement:ID:...|h[Name]|h
+    Url,                // https://... URL
+};
+
+/**
+ * A single parsed segment of a chat message.
+ */
+struct ChatSegment {
+    SegmentType type    = SegmentType::Text;
+    std::string text;           // display text (or URL)
+    ImVec4      color   = ImVec4(1, 1, 1, 1);  // explicit color (for ColoredText / links)
+    uint32_t    id      = 0;    // itemId / spellId / questId / achievementId
+    uint32_t    extra   = 0;    // quest level (for QuestLink)
+    std::string rawLink;        // full original markup for shift-click insertion
+};
+
+/**
+ * Parses raw WoW-markup text into a flat list of typed segments.
+ *
+ * Extracted from ChatPanel::render() inline lambdas (Phase 2.1 of chat_panel_ref.md).
+ * Pure logic — no ImGui calls, no game-state access. Fully unit-testable.
+ */
+class ChatMarkupParser {
+public:
+    /** Parse a raw chat message string into ordered segments. */
+    std::vector<ChatSegment> parse(const std::string& rawMessage) const;
+
+    /** Parse |cAARRGGBB color code at given position. */
+    static ImVec4 parseWowColor(const std::string& text, size_t pos);
+};
+
+} // namespace ui
+} // namespace wowee