Problem: Highlight inspection is limited to a single position, and its
result types do not document the fields shared by different highlight
sources.

Solution: Accept end_row/end_col in vim.inspect_pos to inspect a range.
Keep range ends exclusive and retain the existing single-position
behavior.

Support Ex line ranges in :Inspect, including Visual selections.
Document named result types, expose shared highlight fields, and keep
the existing extmark details and buffer field for compatibility.

AI-assisted

Problem: Argument type mismatches are excluded from EmmyLua checks.

Solution: Correct runtime annotations and calls, document local checker
workarounds, and enable the diagnostic.

AI-assisted

AI-assisted

Enable EmmyLua's need-check-nil diagnostic and resolve nullable values
through more precise types, explicit invariants, and guards for missing
runtime state. Keep analyzer-specific workarounds local and update the
affected API documentation.

Exclude the bundled re.lua from analysis so its nil-check warnings do
not fail CI.

AI-assisted

Other (squashed) commits:

fix(tui): emit ui_send output atomically with the frame

Problem:
tui_ui_send() writes directly to the TTY, bypassing the output buffer.
Sequences sent via nvim_ui_send() (e.g. kitty multiple-cursors, or
visual-dot-repeat) always arrive in a separate TTY write from the frame
they were computed for. This manifests as "tearing", or e.g. in the case
of multicursor the terminal renders text with stale cursor overlays.

Solution:
- tui_ui_send(): while a frame is being assembled (pending invalid
  regions or buffered output), buffer instead of writing directly.
  - Out-of-frame sends (tty queries, clear-on-disable) still write
    immediately.
- mcursor.lua: emit the terminal-cursor update at the end of the redraw
  cycle (`on_end`, when screen positions are final) instead of
  vim.schedule().

Problem:
After #40270, events are no longer emitted from the automatic background
detection. This applies not just during startup, but also if the user
manually changes the background of their terminal.

Solution:
Set the background as normal, assuming that a normal terminal will
respond within 100 ms. Change test to match expected behavior:
- BG set during startup won't trigger user autocmds since it runs before
  any user config
- If the terminal takes longer than 100 ms to respond to initial OSC 11,
  it does trigger the OptionSet, but it is triggered through the normal
  path to ensure values like v:option_new are set #38551
- BG change after startup still triggers autocmds #41146

Problem:
Cannot assign Lua functions/closures to "func" ('completefunc',
'tagfun', …) or "expr" ('foldexpr', 'indentexpr', …) options.

Solution:
- Store "func"/"expr" options as `Callback` instead of string.
- Delete oceans of copy-pasted code.
- BREAKING: LuaRef returned via RPC/Vimscript is now represented as
  `"<Lua N: file:line>"` (like what `:map` shows) instead of `nil`.
- Note: `man.vim` still uses `v:lua` string, bc it's a vimscript ftplugin.

Helped-by: Lewis Russell <lewis6991@gmail.com>

Problem:
POSIX-compatible Ex-mode requires special-cases all over the codebase to
match various quirks that don't actually matter to users.
- The main utility of *interactive* Ex-mode is its REPL behavior, and
  that can be achieved with `cmdwin`, which also gains extra UX
  benefits.
- The main utility of *non-interactive* `nvim -es` is for shell
  scripting, where Ex-mode quirks are mostly unhelpful (e.g. the
  "Entering Ex mode" message).

Solution:
- Reimplement *interactive* Ex-mode as a "persistent, insert-mode
  cmdwin" in Lua.
  - "nvim -e/-E" is simply an alias to "gQ".
- Reframe *non-interactive* Ex-mode (`nvim -es`) as "script mode".
  - Drop POSIX Ex-mode quirks.

Improvements:
- "nvim -V1 -es" output ends with a final newline!
- "nvim -V1 -es" no longer shows the "Entering Ex mode" msg. (This was
  pointless noise, unwanted for scripting purposes.)
- stdin is no longer typeahead. Scripts (":lua io.read()") can read
  stdin as data.
- Empty line is a no-op: a stray blank line no longer moves the cursor
  (deviates from POSIX ex "+1"), no longer exits 1 at EOF (E501).

Preserved behavior:
- cursor starts at "$"
- mode()=="cv" (for non-interactive)
- multiline commands (:append/:function/heredoc pull continuation lines)
- bare-range print
- :print=>stdout
- -V1=>stderr
- CRLF input
- continue-after-error and exit codes

Dropped (regressed) POSIX behavior (non-interactive):
- Event loop only ticks while/between commands, not while blocked
  waiting for a stdin line.
- ":g/pat/visual...Q"
- input()/getchar()/":s/x/y/c" no longer consume stdin lines as
  answers: Nvim stops at end-of-input, skipping the rest of the script,
  exit 0. Use ":lua io.read()" instead.
  - If users care about this they should use interactive Ex-mode (`gQ`).
- ":@r" stops at end of the register instead of continuing to read
  cmdline input from stdin.