Add {.topic} markup for non-function help page references

Replace {.code ?AMR-options} and backtick-style ?AMR-options / ?AMR-deprecated
references with proper {.topic AMR-options} / {.topic AMR-deprecated} cli markup
in count.R, interpretive_rules.R, proportion.R, and zz_deprecated.R.

Add {.topic} fallback handler to format_message() in aa_helper_functions.R:
plain-text environments render {.topic foo} as ?foo, and the [text](topic)
link form extracts just the display text (same pattern as {.help}).

Also convert remaining backtick function/arg references in proportion.R to
{.help [{.fun ...}](AMR::...)}, {.arg}, and {.code} markup for consistency.

Note: zzz.R intentionally keeps the backtick form since its startup message
goes through packageStartupMessage() which bypasses our cli infrastructure.

https://claude.ai/code/session_01XHWLohiSTdZvCutwD7ag2b

R/aa_helper_functions.R

@@ -465,6 +465,11 @@ cli_to_plain <- function(msg, envir = parent.frame()) {
     m <- regmatches(c, regexec("^\\[(.*)\\]\\([^)]*\\)$", c, perl = TRUE))[[1L]]
     if (length(m) >= 2L) m[2L] else paste0("`", resolve(c), "`")
   })
+  msg <- apply_sub(msg, "\\{\\.topic ([^}]+)\\}", function(c) {
+    # Handle [display text](topic) markdown link format: extract just the display text
+    m <- regmatches(c, regexec("^\\[(.*)\\]\\([^)]*\\)$", c, perl = TRUE))[[1L]]
+    if (length(m) >= 2L) m[2L] else paste0("?", resolve(c))
+  })
   msg <- apply_sub(msg, "\\{\\.url (\\{[^}]+\\}|[^}]+)\\}",    function(c) resolve(c))
   msg <- apply_sub(msg, "\\{\\.href ([^}]+)\\}",                function(c) strsplit(resolve(c), " ", fixed = TRUE)[[1L]][1L])