Problem:
With these two lines (`\b` marking a backspace):

    f\bfoo
    xb\bb

line 1's bold run ends at byte 1 and line 2's begins at byte 1, so line 1
renders "fo" in bold rather than "f", and line 2's "b" is not bold at all.

Solution:
Only grow a highlight group that is on the current row.

Problem:
man -w echoes any existent file back unchanged. :Man rejected all such
paths, so :Man /usr/share/man/man1/bash.1 failed even for real man pages.

Solution:
Accept an echoed path when it looks like a man page (.../man1/foo.1).

Problem:
On NetBSD, `man -w open` can return the exact manpage path, but `:Man`
may still fail when man directories cannot be discovered from `manpath
-q`, bare `man -w`, or `$MANPATH`.

Solution:
Fall back to the direct manpage lookup when directory discovery fails.
Add a test for resolving `open(2)` through `goto_tag()` without manpath
data.

Problem:
The magic globals `it`, `describe`, etc., are more trouble than they are
worth.

- Hooking into `after_each` requires `getfenv()` hacks.
- They confuse luals/emmylua, because the top-level `.luarc.json` isn't
  merged with `test/.luarc.json` (apparently a luals limitation?)
- They totally defeat discoverability because the user just has to
  "know" about the various magic symbols.

So they harm DX, which means they serve no purpose at all.

Solution:
- Expose the test API from `testutil`, so tests can call `t.it()`,
  `t.describe()`, etc., in the conventional way.
- Drop `getfenv()` hacks.
- Drop the `setfenv()` injection in `load_chunk`.
- Drop `test/_meta.lua`.

Problem:
Listing individual "skipped" notices for each non-actionable or
NVIM_TEST_INTEG test is noisy and makes the "skipped" list overwhelming
and less meaningful.

Solution:
- Mark non-actionable tests with "N/A".
- Report NVIM_TEST_INTEG tests as a separate 1-line summary.

Problem:
cirrus will shutdown soon, and we are running out of minutes anyway,
which causes ci failures.

Solution:
Drop cirrus config.

Problem:
`nvim -l` prints an extra `\r` to stdout:

    :=vim.system({'cmd', '/c',  "echo print(1) | nvim -l -"}, {}):wait()
    {
      code = 0,
      signal = 0,
      stderr = "1\r\r\n",
      stdout = ""
    }

Solution:
Check `headless_mode` in `msg_use_crlf`.

Co-authored-by: Justin M. Keyes <justinkz@gmail.com>

Problem:
Under certain circumstances (e.g. gzipped manpages with mandoc),
:Man will not find the correct page because it does not process
multiple extensions correctly.
For example, with a file named strcpy.3p.gz, it will only check the .gz
part to try to check the section.
This leads to some pages being inaccessible because it will return the
page from the wrong section.

Solution:
Loop and try multiple extensions to try to find one which matches
the name of the section.
Also refactor the man.get_path function so that it can be tested.

"Error" in error messages is redundant. Just provide the context, don't
say "Error ...".

Problem: When piping raw manpage content into `:Man!`, buf name is
set to 'man://.. ref', but the check only matches the prefix.
Allows duplicate buffers to be created, triggering E95.

Solution: Match full buf name instead of only 'man://' prefix.
If the buffer already exists, generate a unique name with
'man://' .. 'ref' .. '?new=' format.

Refs: #30132