refactor(config): default icons to ascii (#55)

* refactor(config): default icons to ascii

Problem: default icons used unicode characters (○, ✓, ●, ▸, ·, ↺)
which render poorly in some terminals and font configurations.

Solution: replace defaults with ascii equivalents (-, x, !, >, ., ~).
Users can still override to unicode or nerd font icons via config.

* ci: ignore library type checking

.luarc.json

@@ -2,6 +2,7 @@
   "runtime.version": "LuaJIT",
   "runtime.path": ["lua/?.lua", "lua/?/init.lua"],
   "diagnostics.globals": ["vim", "jit"],
+  "diagnostics.libraryFiles": "Disable",
   "workspace.library": [
     "$VIMRUNTIME/lua",
     "${3rd}/luv/library",