wip: add long message helpers and payload type controls

- add centralized message validation errors
- switch command handlers to return error
- add explicit long plain-text reply helpers
- support strict payload type policy with debug logging
- document versioning and changelog workflow

keyboard.go

@@ -136,14 +136,22 @@ func NewInlineKeyboard(payloadType BotPayloadType, maxRow int) *InlineKeyboard {
 	}
 }
 
-// SetPayloadType sets the serialization format for callback data added via
+// SetPayloadType sets the keyboard-local serialization format for callback data added via
 // AddCallbackButton and AddCallbackButtonStyle methods.
-// It should be one of BotPayloadJson or BotPayloadBase64.
+// It overrides the bot's default payload type for this keyboard only.
 func (in *InlineKeyboard) SetPayloadType(t BotPayloadType) *InlineKeyboard {
 	in.payloadType = t
 	return in
 }
 
+// GetPayloadType returns the keyboard-local callback payload encoding type.
+func (in *InlineKeyboard) GetPayloadType() BotPayloadType { return in.payloadType }
+
+func (in *InlineKeyboard) SetMaxRow(maxRow int) *InlineKeyboard {
+	in.maxRow = maxRow
+	return in
+}
+
 // Internal helper that appends a button and auto-flushes a full row.
 func (in *InlineKeyboard) append(button tgapi.InlineKeyboardButton) *InlineKeyboard {
 	if in.CurrentLine.Len() == in.maxRow {