fix: make right-click mouse work in Neovim 0.12+

In Neovim 0.12+, normal! with mouse key events (<LeftMouse>,
<LeftRelease>) is restricted and cannot be used to replay mouse events.
This caused E492 errors in s:RightRelease.

Fixes:
- s:MousePress: use wincmd w + cursor() for Neovim instead of
  normal! \<LeftMouse>
- s:MiddleRelease: skip normal! \<LeftRelease> for Neovim
- s:RightRelease: skip normal! \<LeftRelease> for Neovim (root cause
  of the reported E492 error in issue #1)

Co-authored-by: Matěj Cepl <mcepl@cepl.eu>

Author: Copilot

plugin/acme.vim

@@ -980,7 +980,12 @@ function s:MousePress(mode)
 	if s:clickstatus != 0 || s:click.winid == 0
 		return
 	endif
-	exe "normal! \<LeftMouse>"
+	if has('nvim')
+		exe win_id2win(s:click.winid).'wincmd w'
+		call cursor(s:click.line, s:click.column)
+	else
+		exe "normal! \<LeftMouse>"
+	endif
 	let s:visual = s:SaveVisual()
 	let s:clicksel = s:clickmode == 'v' && win_getid() == s:clickwin &&
 		\ s:InSel()
@@ -1001,7 +1006,9 @@ function s:MiddleRelease(click)
 		endif
 		return
 	endif
-	exe "normal! \<LeftRelease>"
+	if !has('nvim')
+		exe "normal! \<LeftRelease>"
+	endif
 	let cmd = a:click <= 0 || s:clicksel ? s:Sel()[0] : expand('<cWORD>')
 	let vis = s:clickmode == 'v' && (a:click <= 0 || !s:clicksel)
 	call s:RestVisual(s:visual)
@@ -1047,7 +1054,9 @@ function s:RightRelease(click)
 		endif
 		return
 	endif
-	exe "normal! \<LeftRelease>"
+	if !has('nvim')
+		exe "normal! \<LeftRelease>"
+	endif
 	let cmd = a:click <= 0 || s:clicksel ? s:Sel()[0] : expand('<cWORD>')
 	let vis = s:clickmode == 'v' && (a:click <= 0 || !s:clicksel)
 	call s:RestVisual(s:visual)