Problem: Custom ui2 window tracks 'fillchars' option to adjust to the
  change of `msgsep` flag. However, 'fillchars' is `:h global-local`
  window option. If it is set locally to the window, ui2 reacts to its
  `msgsep` value and keeps using it afterwards even in other windows.

Solution: Use and react to only global value of 'fillchars'.

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:
After clearing cursors, "]C" "[C" do nothing, although the previous
cursor positions ("gQ") may still be useful as marks.

Solution:
If multicursor is not active, "]C" "[C" iterate the
"nvim.multicursor.last" extmarks. They also work as an operator motion
("d]C"), since there is no cascade.

AI-assisted

Problem:
Only the stdio channel can "own" a server (self-exit on close). After
:restart the TUI reconnects over a socket, so the restarted server does
not have "self-exit" behavior when the channel closes (e.g. by UI
disconnect, host-terminal close, etc.), which leaves a dangling server.

Solution:
- Introduce `nvim_chan_set`. (`nvim_set_client_info` doesn't fit:
  exposing it to Lua would require a `channel` param, which is not
  backwards-compatible, plus it's awkward because it doesn't merge info.)
- Broadcast per-channel properties in the "restart" UI event as an
  opaque dict (a potentially useful pattern for other UI-events in the
  future).
  - UIs are expected to restore the channel properties on restart.
- `nvim_get_chan_info()` reports "detach".
- Remove `nvim__chan_set_detach()`.

Problem:
`vim._with({ buf = 0, win = 0 }, f)` fails an assert in ctx_switch().
vim._with() allows `buf` with `win` when `win` shows `buf`, but
nlua_with() passes both, and ctx_switch() takes only one target.

Solution:
Ignore `buf` if `win` is given; the window implies its buffer.

Problem:
When repeating search using a semicolon (e.g. `/pat1/;/pat2`), `pat`
advances past both the semicolon and the delimiter ('/' or '?'),
consuming 2 characters, but `patlen` was only decremented by 1.
Consequently, `patlen` in the subsequent search is 1 byte too long and
includes the trailing NUL byte, corrupting `msgbuf` and causing ui2's
search_count handler to fail with 'attempt to concatenate a nil value'.

Solution:
Decrement `patlen` by 2 when skipping ';' and delimiter. Also ensure
ui2 safely guards search_count messages when extracting the search stat.

Fixes #41929

AI-assisted

Problem:

- annotation-usage-error and code-style-check are disabled.
- vim.inspect relies on a dummy self-assignment for docgen, and its help
  omits parameter and option details.
- LuaLS fallback types obscure iterator inference.
- Docgen hardcodes public function names and appends separately sorted
  files, leaving shared helpers under the inspector heading.

Solution:

- Enable annotation-usage-error and code-style-check, and fix misplaced
  annotations.
- Document vim.inspect's callable module directly, removing the dummy
  assignment. Describe its parameters, option defaults and process
  callback.
- Remove LuaLS iterator fallbacks, correct iterator signatures and check
  values that the improved inference identifies as optional.
- Parse callable modules, require bindings and parent module references.
  Derive public names and inherited function docs from these links,
  including missing help for vim.async.semaphore() and vim.version().
- Export vim.lsp.tagfunc directly with lazy loading and document its
  implementation instead of maintaining a wrapper.
- Group files in section_order, replacing append_only and merge_files.
  Merge declarations before sorting each section, placing shared helpers
  in the main vim section and keeping vim.inspect in alphabetical order.
- Add basic parser coverage for callable modules and module links.

AI-assisted

Problem:
`nvim_mcursor` is not fully baked, and not strongly motivated,
currently. The main programmatic interface for cursors is the
"nvim.multicursor" extmarks namespace.

Solution:
Drop `nvim_mcursor`. Add an internal hook so that multicursor can react
when extmarks are added to the "nvim.multicursor" namespace.

TODO:
If extmarks/namespaces are clumsy to work with, we should _fix that_
rather than adding wrappers.

fix(lua): enable param-type-mismatch diagnostic

Problem:
- `[count]Q` and `{Visual}Q` are implemented as ad hoc utils, because
  `Q` is not an "operator".
- `Q` always "toggles", it is not "idempotent".
- Various *cursor-relative* marks (`'.`, `'[`) are not saved/restored
  per-cursor, so they don't work during cascade.
- Insert cascade clobbers the primary's `'^` and changelist.

Solution:
- Introduce the `zq{motion}` operator, which places cursors at every
  reachable `{motion}`.
  - `{Visual}Q` is now an alias to `{Visual}zqj`.
- Introduce `1Q` and `2Q` for idempotent cursor placement.
  - Drop `[count]Q`, it's redundant with `zqgn`.
- Classify cursor-relative marks as `type=motion` instead of
  `type=jump`. Save/restore per-cursor during cascade.