Replace bare backticks with cli inline markup across all messaging calls

- {.arg} for argument names in stop_/warning_/message_ calls
- {.cls} after "of class" text in format_class() and elsewhere
- {.fun} for function names (replaces `fn()` pattern)
- {.pkg} for tidyverse package names (dplyr, ggplot2)
- {.code} for code literals (TRUE, FALSE, expressions)
- Rewrite print.ab: use cli named-vector with * bullets and code
  highlighting when cli >= 3.0.0; keep plain-text fallback otherwise
- Fix typo in as.sir(): "of must be" -> "or must be"
- switch sir.R verbose notes from message() to message_()

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/av_property.R

@@ -233,12 +233,12 @@ av_url <- function(x, open = FALSE, ...) {
 
   NAs <- av_name(av, tolower = TRUE, language = NULL)[!is.na(av) & is.na(atcs)]
   if (length(NAs) > 0) {
-    warning_("in `av_url()`: no ATC code available for ", vector_and(NAs, quotes = FALSE), ".")
+    warning_("in {.fun av_url}: no ATC code available for ", vector_and(NAs, quotes = FALSE), ".")
   }
 
   if (open == TRUE) {
     if (length(u) > 1 && !is.na(u[1L])) {
-      warning_("in `av_url()`: only the first URL will be opened, as `browseURL()` only suports one string.")
+      warning_("in {.fun av_url}: only the first URL will be opened, as {.fun browseURL} only suports one string.")
     }
     if (!is.na(u[1L])) {
       utils::browseURL(u[1L])