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

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

Problem:
Servers cannot request refreshing stale LSP folding ranges after a
project-wide change.

Solution:
Advertise `workspace.foldingRange.refreshSupport` and re-request folding
ranges for active buffers when handling `workspace/foldingRange/refresh`.

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

Problem: LuaLS struggles with the generics used in Nvim's runtime,
requiring broad diagnostic suppressions. Indexing is also slow.

Solution: Use EmmyLua for type checks in the build and CI. It offers
more sophisticated type checking, substantially better support for
generics, and much better flow analysis.

Correct the affected annotations. Use `@internal`, supported directly by
EmmyLua, instead of `@nodoc` for shared internal declarations, and
support it in the help parser.

AI-assisted

Problem:
Folding range markers are overwritten while ranges are evaluated. A range ending on a row can hide another range starting there, and multiple nested ranges ending together emit only the innermost ending level.

Solution:
Track starts and the number of ends per row before emitting markers. Prefer starts on shared boundary rows and use the outermost level when nested ranges end together.

AI-assisted

Problem: Every LSP capability that sends a request on a document change
to update its state was using its own buffer-local autocmd to do so.
That means there is a separate autocmd per buffer per active
capability/feature, and the actual code inside the autocmd callback was
virtually identical. The same problem occurred for capabilities that had
components to draw on the screen that had their own decoration providers.

Solution: Introduce a central `LspNotify` autocmd and decoration
provider in the capability module itself. New base class methods
`on_close` and `on_change` that take a client_id have been provided, for
`didClose` and `didOpen`/`didChange` notifications respectively. New
base class method `on_win` that takes topline and botline has been
provided to add extmarks or perform other work when lines of a buffer
are being drawn.

The autocmd callback loops through each active capability instance for
the buffer and calls a corresponding method with the triggering
client_id if it is currently attached to the buffer that triggered the
autocmd. The decoration provider just calls on_win for all active
capabilities on the buffer.

This slightly tweaks folding range to make use of these new client-id
specific callbacks.