Also update the type annotation of TSNode:id(), which returns a string,
not an integer.

Problem:  No test for mode() when executing Ex commands
Solution: Add some test cases and simplify several other test cases.
          Also add a few more test cases for ModeChanged.

closes: vim/vim#13588

https://github.com/vim/vim/commit/fcaeb3d42b228e73c669b2fce78f1d3fe112769f

feat(decoration): allow conceal_char to be a composing char

decor->text.str pointer must go. This removes it for conceal char,
in preparation for a larger PR which will also handle the sign case.

By actually allowing composing chars for a conceal chars, this
becomes a feature and not just a refactor, as a bonus.

Problem:  Cannot detect overstrike mode in Cmdline mode
Solution: Make mode() return "cr" for overstrike

closes: vim/vim#13569

https://github.com/vim/vim/commit/d1c3ef1f47c87d1da056c56564e1985fe6f2931d

close #25416

`vim.wait()` cannot be called in a fast callback since the main loop
cannot be run in that context as it is not reentrant

Fixes #26122

closes #24141
closes #24746