Fix {.help} markup to use correct cli link format [{.fun fn}](AMR::fn)

Replace all instances of {.help AMR::fn}() (incorrect format with manual
parentheses outside the link) with {.help [{.fun fn}](AMR::fn)} which is
the correct cli hyperlink syntax: the display text [{.fun fn}] renders the
function name with parentheses automatically, and (AMR::fn) is the link target.

Also update the plain-text fallback handler in aa_helper_functions.R to
extract the display text from the [text](topic) markdown link format,
so that non-cli environments show just the function name (e.g. `fn()`),
not the raw link markup.

Dynamic cases in amr_selectors.R and mo_property.R also updated.

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/mo_property.R

@@ -1043,7 +1043,7 @@ find_mo_col <- function(fn) {
   )
   if (!is.null(df) && !is.null(mo) && is.data.frame(df)) {
     if (message_not_thrown_before(fn = fn)) {
-      message_("Using column '", font_bold(mo), "' as input for {.help AMR::", fn, "}()")
+      message_("Using column '", font_bold(mo), "' as input for {.help [{.fun ", fn, "}](AMR::", fn, ")}")
     }
     return(df[, mo, drop = TRUE])
   } else {