Modernise messaging infrastructure with cli support

Rewrites message_(), warning_(), stop_() to use cli::cli_inform(),
cli::cli_warn(), and cli::cli_abort() when the cli package is available,
with a fully functional plain-text fallback for environments without cli.

Key changes:
- New cli_to_plain() helper converts cli inline markup ({.fun}, {.arg},
  {.val}, {.field}, {.cls}, {.pkg}, {.href}, {.url}, etc.) to readable
  plain-text equivalents for the non-cli fallback path
- word_wrap() simplified: drops add_fn, ANSI re-index algorithm, RStudio
  link injection, and operator spacing hack; returns pasted input unchanged
  when cli is available
- stop_() no longer references AMR_env$cli_abort; uses pkg_is_available()
  directly; passes sys.call() objects to cli::cli_abort() call= argument
- Removed add_fn parameter from message_(), warning_(), and word_wrap()
- All call sites across R/ updated: add_fn arguments removed, some paste0-
  based string construction converted to cli glue syntax ({.fun as.mo},
  {.arg col_mo}, {n} results, etc.)
- cli already listed in Suggests; no DESCRIPTION dependency changes needed

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/mo_source.R

@@ -129,7 +129,7 @@ set_mo_source <- function(path, destination = getOption("AMR_mo_source", "~/mo_s
 
   meet_criteria(path, allow_class = "character", has_length = 1, allow_NULL = TRUE)
   meet_criteria(destination, allow_class = "character", has_length = 1)
-  stop_ifnot(destination %like% "[.]rds$", "the `destination` must be a file location with file extension .rds.")
+  stop_ifnot(destination %like% "[.]rds$", "the {.arg destination} must be a file location with file extension .rds.")
   mo_source_destination <- path.expand(destination)
 
   if (is.null(path) || path %in% c(FALSE, "")) {
@@ -137,7 +137,6 @@ set_mo_source <- function(path, destination = getOption("AMR_mo_source", "~/mo_s
     if (file.exists(mo_source_destination)) {
       unlink(mo_source_destination)
       message_("Removed mo_source file '", font_bold(mo_source_destination), "'",
-        add_fn = font_red,
         as_note = FALSE
       )
     }
@@ -250,7 +249,7 @@ get_mo_source <- function(destination = getOption("AMR_mo_source", "~/mo_source.
     current_ext <- regexpr("\\.([[:alnum:]]+)$", destination)
     current_ext <- ifelse(current_ext > -1L, substring(destination, current_ext + 1L), "")
     vowel <- ifelse(current_ext %like% "^[AEFHILMNORSX]", "n", "")
-    stop_("The AMR mo source must be an RDS file, not a", vowel, " ", toupper(current_ext), " file. If `\"", basename(destination), "\"` was meant as your input file, use `set_mo_source()` on this file. In any case, the option `AMR_mo_source` must be set to another path.")
+    stop_("The AMR mo source must be an RDS file, not a{vowel} {toupper(current_ext)} file. If \"{basename(destination)}\" was meant as your input file, use {.fun set_mo_source} on this file. In any case, the option {.code AMR_mo_source} must be set to another path.")
   }
   if (is.null(AMR_env$mo_source)) {
     AMR_env$mo_source <- readRDS_AMR(path.expand(destination))