Qualify all {.help} tags with AMR:: and convert backtick ?func references

- Add AMR:: namespace prefix and trailing () to all {.help} cli markup
  so they render as clickable help links (e.g. {.help AMR::as.sir}())
- Convert `?funcname` backtick-quoted help references to {.help AMR::funcname}()
  in aa_helper_functions.R, custom_eucast_rules.R, interpretive_rules.R,
  key_antimicrobials.R, mo.R, plotting.R, resistance_predict.R, and sir.R
- Skipped `?proportion` in sir_calc.R as 'proportion' is not exported

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/key_antimicrobials.R

@@ -187,7 +187,7 @@ key_antimicrobials <- function(x = NULL,
           "No columns available ",
           paste0("Only using ", values_new_length, " out of ", values_old_length, " defined columns ")
         ),
-        "as key antimicrobials for ", name, "s. See `?key_antimicrobials`."
+        "as key antimicrobials for ", name, "s. See {.help AMR::key_antimicrobials}()."
       )
     }