fix: Djot user-defined pseudo-symbols nesting issue

packages/markdown/commands.lua

@@ -103,7 +103,7 @@ local function decimalFilter (input, _)
 end
 
 local function wrapLinkContent (options, content)
-  local passedOptions = pl.tablex.copy(options) -- shallow
+  local passedOptions = pl.tablex.copy(options) -- shallow before removing internal options
   -- We already took care of these.
   passedOptions.src = nil
   passedOptions.id = nil
@@ -247,7 +247,7 @@ function package:registerCommands ()
         -- We'll want the ID to apply to the captioning environment (to potentially
         -- use the caption numbering)
         local id = image.options.id
-        image.options.id = nil
+        image.options.id = nil -- FIXME should we shallow copy options before changing fields? (Case of re-use via pseudo-symbols)
         -- We also propagate image options to the englobing environment
         SILE.call("markdown:internal:captioned-figure", image.options, {
           image,
@@ -508,7 +508,7 @@ Please consider using a resilient-compatible class!]])
       if not (self.hasPackageSupport.piecharts or self.hasPackageSupport.piechart) then -- HACK Some early versions of piecharts have the wrong internal name
         SU.error("No piecharts package available to render CSV data ".. uri)
       end
-      options.src = nil
+      options.src = nil -- FIXME should we shallow copy options before changing fields? (Case of re-use via pseudo-symbols)
       options.csvfile = uri
       SILE.call("piechart", options)
     else
@@ -848,6 +848,7 @@ Please consider using a resilient-compatible class!]])
       local text = ":" .. symbol .. ":"
       content = { text }
     end
+    options = pl.tablex.copy(options) -- shallow before removing internal options
     options._symbol_ = nil
     options._standalone_ = nil
     if next(options) and not standalone then