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

- call-non-callable
- missing-fields
- redefined-label
- redefined-local
- undefined-field
- unreachable-code

Promote redefined-local and unreachable-code to warnings.

Fix DOS line-ending handling for multiline semantic tokens, and support
intersection types in the help parser.

AI-assisted

Close #38748
Close #38866

Co-authored-by: Mario Loriedo <mario.loriedo@gmail.com>
Co-authored-by: Anakin Childerhose <anakin@childerhose.ca>

Problem
Cannot specify headers in vim.net.request() call.

Solution
Support opts.headers in vim.net.request opts.

Problem:
Apparently vim.SystemCompleted.stdout can also be nil, even without a
custom stdout handler. (Although the docs can be interpreted otherwise).

Solution:
Explicitly check for nil and set the result body to an empty string if
stdout was nil.

Problem:
on_response(err, response) handler doesn't receive a response when an
output buffer or path is supplied to vim.net.request. User might want to
both output output to a file/buffer and also do something with it on
response.

Solution:
If an on_response handler was given, then pass the response to it.