Problem: Repeated default fields and field-by-field assertions obscure
the values that each functional test is meant to check.

Solution: Add eq_partial() to check selected record fields while
preserving list length and order. Use local helpers to fill fixed
expected defaults where tests need full equality. Keep explicit absence
checks and test-specific values at the call sites.

AI-assisted

vim-patch:9.2.1114: Visual selection is not highlighted at the cursor position

Problem:  In a terminal the character under the cursor is normally not
          shown as part of the visual selection.
Solution: Don't set "noinvcur" in win_line() (Shane Harper).

The problem did not occur in the GUI, only in a terminal.

The name "noinvcur" ("don't invert the cursor") was misleading: the
variable did not affect the cursor, but whether the character under the
cursor could be displayed as part of the visual selection.

The "noinvcur" handling may have been meant to help during a visual
selection when Visual is shown in reverse video and the terminal draws
the cursor by inverting the character under it, as otherwise the
character under the cursor would not look highlighted like the rest of
the selection. But Vim cannot know in general how a terminal draws the
cursor, and when either the cursor is not drawn by inverting the
character under it or Visual is not shown in reverse video, the handling
just left a character of the visual selection unhighlighted.

closes: vim/vim#21317

https://github.com/vim/vim/commit/d10aab4ba6602f8f2f2576d2d62ceb63869db6fb

Co-authored-by: Shane Harper <shane@shaneharper.net>
AI-assisted

Problem: Traditionally, the ruler in the last line is one cell shorter
than in the statusline, leaving the last cell of the screen blank.
According to code comments, this is in order to prevent unwanted
scrolling on "some" (unspecified, but presumably ancient) terminals.
Berkeley vi is more specific in its `vs_modeline` function: dumb
terminals with hardware scroll, SunOS 4.1.1 and Ultrix 4.2 curses.
(n)curses still has a similar limitation in `(w)addstr`, but apparently
only for historical reasons.

Maintaining the different widths leads to awkward inconsistencies when
the ruler is configured with 'rulerformat', except for the special case
where it contains a top-level `%=`. Shifting the ruler in the last line
to the left would be a solution, but the empty cell at the end doesn't
seem to be relevant anymore.

Solution: extend the ruler in the last line all the way to the right
edge of the screen, just like in the statusline. The exact same amount
of place will be available to the rest of the UI as before.

BREAKING CHANGE:
- the default ruler width is now 18 cells
- the last cell of the screen is no longer empty

Closes #41076

Problem:
Cursor-relative floats can use stale screen coordinates after a cursor move is restored without a redraw.

Solution:
Validate the current cursor before converting cursor-relative coordinates.

Co-authored-by: zeertzjq <zeertzjq@outlook.com>

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:
The title is combined with window's attributes only if the title is a
string (which implies the FloatTitle / FloatFooter highlight groups),
but not when the title is text-hl chunks.

Solution:
Combine specified highlight group with window-local Normal highlight as
well.

Problem:
Float border highlight groups (FloatBorder, FloatTitle and FloatFooter)
fall back to Normal background highlight if no background color set.

Solution:
Combine border colors with window-local Normal highlight.

Fix #38330

Problem: #40731 may still crash if close_buffer autocmds reinsert the float's
grid. Plus removing the grid (and posting win_close) is unneeded if
win_close_othertab refuses to close the window later, which is possible.

Solution: do the stuff before freeing the window, like win_close.

Problem: Closing a floating window from a non-current tab frees its grid
without removing it from the compositor's `layers` table, so the next
`ui_comp_put_grid()` walks a dangling pointer (UAF).

Solution: Call `ui_comp_remove_grid()` (and `ui_call_win_close()` for
multigrid UIs) before `win_free_mem()`, matching `win_close()` since
PR #21551.