Add Tetris Only practice mode

[Knuckleykong]

Add Tetris Only mode

New practice mode where:

• Tetrises score normally.
• Singles, doubles, and triples subtract their normal point value.
• Score is clamped at zero.

Implementation

• Added MODE_TETRISONLY.
• Added a menu entry for Tetris Only.
• Added Tetris Only scoring logic.
• Refactored line-clear point calculation into a shared helper.

Menu

Adding an additional game mode required a menu alignment adjustment so menu selections continue to correspond to the correct mode after reducing the number of blank rows at the top of the menu.

[Knuckleykong]

Note: On my local machine, build.js reports a Node.js
"invalid table size / heap out of memory" error after the
link step, although the ROM is successfully generated and
functions correctly. I have not yet determined whether this
is environment-specific.

[zohassadar]

Note: On my local machine, build.js reports a Node.js "invalid table size / heap out of memory" error after the link step, although the ROM is successfully generated and functions correctly. I have not yet determined whether this is environment-specific.

This problem appears to be introduced in node 26.3.0 and is related to this loop:

TetrisGYM/tools/patch/bps.js

Lines 96 to 109 in ab8628c

	while(file.offset<endActionsOffset){
	var data=file.readVLV();
	var action={type: data & 3, length: (data >> 2)+1};
	if(action.type===BPS_ACTION_TARGET_READ){
	action.bytes=file.readBytes(action.length);
	}else if(action.type===BPS_ACTION_SOURCE_COPY || action.type===BPS_ACTION_TARGET_COPY){
	var relativeOffset=file.readVLV();
	action.relativeOffset=(relativeOffset & 1? -1 : +1) * (relativeOffset >> 1)
	}
	patch.actions.push(action);
	}

[Knuckleykong]

Ah, other than that issue everything seemed to work as intended. I'm quite bad at Tetris so I'm not able to test the scoring at higher levels but it worked as designed for levels 1 and 2