fix(tui): use 0x7f as Backspace on Windows with VT input (#37679)

Problem:  0x08 is treated as Backspace instead of Ctrl-H on Windows.
Solution: Treat 0x7f as Backspace if VT input is enabled, so that 0x08
          is treated as Ctrl-H.

Ref: https://github.com/microsoft/terminal/issues/4949

src/nvim/tui/input.c

@@ -132,6 +132,9 @@ void tinput_init(TermInput *input, Loop *loop, TerminfoEntry *ti)
   input->ttimeout = (bool)p_ttimeout;
   input->ttimeoutlen = p_ttm;
 
+  // setup input handle
+  rstream_init_fd(loop, &input->read_stream, input->in_fd);
+
   for (size_t i = 0; i < ARRAY_SIZE(kitty_key_map_entry); i++) {
     pmap_put(int)(&kitty_key_map, kitty_key_map_entry[i].key, (ptr_t)kitty_key_map_entry[i].name);
   }
@@ -145,9 +148,6 @@ void tinput_init(TermInput *input, Loop *loop, TerminfoEntry *ti)
   int curflags = termkey_get_canonflags(input->tk);
   termkey_set_canonflags(input->tk, curflags | TERMKEY_CANON_DELBS);
 
-  // setup input handle
-  rstream_init_fd(loop, &input->read_stream, input->in_fd);
-
   // initialize a timer handle for handling ESC with libtermkey
   uv_timer_init(&loop->uv, &input->timer_handle);
   input->timer_handle.data = input;

src/nvim/tui/tui.c

@@ -2515,19 +2515,29 @@ static void flush_buf(TUIData *tui)
 
 /// Try to get "kbs" code from stty because "the terminfo kbs entry is extremely
 /// unreliable." (Vim, Bash, and tmux also do this.)
+/// On Windows, use 0x7f as Backspace if VT input has been enabled by stream_init().
 ///
 /// @see tmux/tty-keys.c fe4e9470bb504357d073320f5d305b22663ee3fd
 /// @see https://bugzilla.redhat.com/show_bug.cgi?id=142659
-static const char *tui_get_stty_erase(int fd)
+/// @see https://github.com/microsoft/terminal/issues/4949
+static const char *tui_get_stty_erase(TermInput *input)
 {
   static char stty_erase[2] = { 0 };
 #if defined(HAVE_TERMIOS_H)
   struct termios t;
-  if (tcgetattr(fd, &t) != -1) {
+  if (tcgetattr(input->in_fd, &t) != -1) {
     stty_erase[0] = (char)t.c_cc[VERASE];
     stty_erase[1] = NUL;
     DLOG("stty/termios:erase=%s", stty_erase);
   }
+#elif defined(MSWIN)
+  DWORD dwMode;
+  if (((uv_handle_t *)&input->read_stream.s.uv)->type == UV_TTY
+      && GetConsoleMode(input->read_stream.s.uv.tty.handle, &dwMode)
+      && (dwMode & ENABLE_VIRTUAL_TERMINAL_INPUT)) {
+    stty_erase[0] = '\x7f';
+    stty_erase[1] = NUL;
+  }
 #endif
   return stty_erase;
 }
@@ -2539,7 +2549,7 @@ static const char *tui_tk_ti_getstr(const char *name, const char *value, void *d
   TermInput *input = data;
   static const char *stty_erase = NULL;
   if (stty_erase == NULL) {
-    stty_erase = tui_get_stty_erase(input->in_fd);
+    stty_erase = tui_get_stty_erase(input);
   }
 
   if (strequal(name, "key_backspace")) {

test/functional/terminal/tui_spec.lua

@@ -2830,7 +2830,6 @@ describe('TUI', function()
   end)
 
   it('<C-h> #10134', function()
-    t.skip(is_os('win'), 'FIXME: does not work on Windows #36660')
     local screen = tt.setup_child_nvim({
       '--clean',
       '--cmd',