fix(mappings): replaying a deleted Lua mapping is UB

Problem:
Replaying a deleted Lua mapping, may call an arbitrary function.

RHS of a Lua mapping embeds its LuaRef (`<K_LUA><ref><CR>`). The raw
keys may outlive the ref (redobuff ".", CmdAtom `keys`). If the mapping
is deleted, replaying it either (1) dereferences a freed registry slot,
or (2) calls whatever callback reused the slot (autocmd, timer, other
mapping).

Solution:
Assign a monotonic (never recycled) id to Lua mappings and encode the
mapping keys as `<K_LUA><id><CR>`.

Note: in the case of Vimscript, a deleted function raises E117, but if
the function is redefined with the same name, the mapping will find it.

Alternatives?:
- Globally ensure `LuaRef` ids are not recycled.
  - Problem: could exhaust `int` in a long-lived Nvim session? Also,
    difficult to impl bc the "recycling" is done by `luaL_ref` itself.

ref: 5ac2e47acc999472042df4f10f8f7b5ffa72ba3e

0 files changed, 0 insertions, 0 deletions