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

Enable EmmyLua's assign-type-mismatch diagnostic after correcting the
runtime annotations and assignments it flags.

Correct option, tuple, and return types, and use separate locals when a
value changes representation. Add guards and narrow casts where needed
so the runtime passes the stricter check. Regenerate the affected docs.

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

Problem:  filetype: icalendar files are not recognized
Solution: Detect *.ics files as icalendar filetype, include
          syntax and filetype plugins (Anakin Childerhose).

Reference:
https://datatracker.ietf.org/doc/html/rfc5545

closes: vim/vim#21356

https://github.com/vim/vim/commit/7c049d5ce1d6bc119abf9749ca5cad74225ca83e

Co-authored-by: Anakin Childerhose <anakin@childerhose.ca>

Problem:  filetype: Gentoo portage config files are not recognized
Solution: Detect portage files as sh or confini filetype
          (Wu, Zhenyu)

Reference:
https://wiki.gentoo.org/wiki//etc/portage/make.conf
https://wiki.gentoo.org/wiki//etc/portage/repos.conf
https://wiki.gentoo.org/wiki//etc/portage/binrepos.conf

closes: vim/vim#21343

https://github.com/vim/vim/commit/2c2bae52ac66dbb8ff13c3842aba64c1b64aa0e5

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

Problem:  filetype: hlsl files are not recognized
Solution: Detect *.hlsl files hlsl filetype, include
          ftplugin, indent and syntax plugins, update
          gvim menu (Maxim Kim)

closes: vim/vim#20993

https://github.com/vim/vim/commit/11fca33162ad2e6a6365dbf6202fb1af0f21b7cb

Co-authored-by: Maxim Kim <habamax@gmail.com>

Problem:  filetype: not all crontab files are recognized
          (efahl)
Solution: Detect crontabs.* as crontab filetype

fixes: vim/vim#21253

https://github.com/vim/vim/commit/86a3567396d6f5fca6b4222363a8201308795a49

Co-authored-by: Christian Brabandt <cb@256bit.org>

Problem:  filetype: evcxr history files are not recognized
Solution: Detect evcxr/history.txt as rust filetype (Wu, Zhenyu).

Reference:
https://github.com/evcxr/evcxr/blob/main/evcxr_repl/README.md

closes: vim/vim#21164

https://github.com/vim/vim/commit/e6bc60ce1b24954ebead198ba0afe41f94bbcf89

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

Enable checks for unused code, deprecated calls, return types, and
annotations.

Fix the warnings and replace the deprecated highlight function. Keep
exceptions where old APIs are still needed or the checker gets it wrong.

AI-assisted