fix(addon-serialize): restore the cursor after a full row without a relative move

[Tongering]

Fixes #6165.

Problem

SerializeAddon restores the cursor with a relative move computed as
realCursorCol - _lastCursorCol. When the serialized stream ends on a full row, the
replayed cursor sits in the pending-wrap sentinel column (cursorX === cols), and
_lastCursorCol is cols as well. A relative CSI n D issued from that state collapses
the sentinel first and then moves, so the cursor lands one column short and all following
output shifts left.

Measured on master: with cursorX === cols, CSI 1 D lands on column 8, while
CSI 10 G lands on column 9.

Minimal repro (also added as a unit test):

	cursor	after writing XY
source	[9, 0]	ABCDEFGHIX / Y
restored (before)	[8, 0]	ABCDEFGHXY / (empty)

Fix

When the tracked column is at or past cols, the column is set with CSI <col+1> G
instead of a relative move.

Why not clamp _lastCursorCol

I first tried clamping the tracked column to cols - 1. That is worse: it discards the
sentinel entirely, so the restored terminal has no pending wrap and the next character
wraps to the following row instead of overwriting the last cell.

Verification

• the new unit test fails on master and passes with the fix
• npm run test-unit -- addons/addon-serialize/out-esbuild/SerializeAddon.test.js → 45 passing
• npm run test-unit → all green
• npm run lint → Found 0 warnings and 0 errors.