Refine help text, keybindings, GUI themes, and undo system.

- Expanded help text and command documentation with detailed keybinding descriptions.
- Added theme customization support to GUIConfig (Nord default, light/dark variants).
- Adjusted for consistent indentation and debug instrumentation in undo system.
- Enhanced test cases for multi-line, UTF-8, and branching scenarios.

Editor.h

@@ -301,22 +301,23 @@ public:
 	}
 
 
- // --- Generic Prompt subsystem (for search, open-file, save-as, etc.) ---
- enum class PromptKind {
-     None = 0,
-     Search,
-     RegexSearch,
-     RegexReplaceFind,  // step 1 of Regex Search & Replace: find pattern
-     RegexReplaceWith,  // step 2 of Regex Search & Replace: replacement text
-     OpenFile,
-     SaveAs,
-     Confirm,
-     BufferSwitch,
-     GotoLine,
-     Chdir,
-     ReplaceFind,  // step 1 of Search & Replace: find what
-     ReplaceWith   // step 2 of Search & Replace: replace with
- };
+	// --- Generic Prompt subsystem (for search, open-file, save-as, etc.) ---
+	enum class PromptKind {
+		None = 0,
+		Search,
+		RegexSearch,
+		RegexReplaceFind, // step 1 of Regex Search & Replace: find pattern
+		RegexReplaceWith, // step 2 of Regex Search & Replace: replacement text
+		OpenFile,
+		SaveAs,
+		Confirm,
+		BufferSwitch,
+		GotoLine,
+		Chdir,
+		ReplaceFind, // step 1 of Search & Replace: find what
+		ReplaceWith, // step 2 of Search & Replace: replace with
+		Command // generic command prompt (": ")
+	};
 
 
 	void StartPrompt(PromptKind kind, const std::string &label, const std::string &initial)
@@ -518,20 +519,38 @@ private:
 	std::string prompt_text_;
 	std::string pending_overwrite_path_;
 
-    // GUI-only state (safe no-op in terminal builds)
-    bool file_picker_visible_ = false;
-    std::string file_picker_dir_;
+	// GUI-only state (safe no-op in terminal builds)
+	bool file_picker_visible_ = false;
+	std::string file_picker_dir_;
 
-    // Temporary state for Search & Replace flow
+	// Temporary state for Search & Replace flow
 public:
-    void SetReplaceFindTmp(const std::string &s) { replace_find_tmp_ = s; }
-    void SetReplaceWithTmp(const std::string &s) { replace_with_tmp_ = s; }
-    [[nodiscard]] const std::string &ReplaceFindTmp() const { return replace_find_tmp_; }
-    [[nodiscard]] const std::string &ReplaceWithTmp() const { return replace_with_tmp_; }
+	void SetReplaceFindTmp(const std::string &s)
+	{
+		replace_find_tmp_ = s;
+	}
+
+
+	void SetReplaceWithTmp(const std::string &s)
+	{
+		replace_with_tmp_ = s;
+	}
+
+
+	[[nodiscard]] const std::string &ReplaceFindTmp() const
+	{
+		return replace_find_tmp_;
+	}
+
+
+	[[nodiscard]] const std::string &ReplaceWithTmp() const
+	{
+		return replace_with_tmp_;
+	}
 
 private:
-    std::string replace_find_tmp_;
-    std::string replace_with_tmp_;
+	std::string replace_find_tmp_;
+	std::string replace_with_tmp_;
 };
 
 #endif // KTE_EDITOR_H