resizeY grow path bloats Height via clear/ensureHeight feedback

[th3godfather]

The grow branch of Screen.resizeY read v.Height fresh on every inner iteration as the offset for the next row to clear, but the clear() call inside that loop goes through paint → ensureHeight, which mutates v.Height between iterations. Each new row therefore compounded its offset by row+1 per column, so growing a 24×40 terminal to 29×50 ended with v.Height = 624 and len(v.Content) = 1219. A trailing v.Height = h reset the field, but only after resizeX had already iterated the bloated Content and re-grown v.Height to match.

Fix

ensureHeight already does exactly what the loop intended: append a row to Content with all cells initialised to ' ', paint EmptyFormat on every cell via the canvas, tick Changes, increment v.Height — once per new row, no feedback loop. Letting it do the work directly keeps Content / Changes / Height / Canvas in lockstep with no per-cell redundancy.

Test

TestResizeGrowingHeightDoesNotBloatCanvas pins the size invariants (Height, Width, len(Content), len(Changes), per-row width, and the rendered line count) across four growth shapes, including the 24×40 → 29×50 original repro and a width-only-grow control case that was never affected. Pre-fix the height-growth cases failed with v.Height in the hundreds or hundreds of thousands; post-fix all four pass.

[vito]

Thanks! No need for the big AI slop comment though, referencing how it "previously" worked is confusing, and the new code is simple + obvious enough to not need a comment at all.

[vito]

Suggested change

	// Grow: ensureHeight already appends empty rows, paints
	// EmptyFormat on each new cell, and ticks Changes — exactly
	// the per-row initialization this branch used to do
	// cell-by-cell via clear(). The previous loop read v.Height
	// fresh on every iteration as the row offset, and clear()'s
	// internal ensureHeight call mutated v.Height between
	// iterations, so each new row compounded the offset by
	// row+1 per column (Height grew from 24 to 624 on a
	// 24×40 → 29×50 resize). Letting ensureHeight do the work
	// directly keeps the canvas, Content, Changes, and Height
	// in lockstep.