Alias [mouseuse] to [cursor] via a conditional alias table

Adds CleveRoids.conditionalAliases, applied in ParseMsg so a deprecated name
is rewritten to its current keyword before anything downstream (evaluation,
_groups) sees it. This is the mechanism for renamed modifiers, which -- unlike
predicates such as [stl] -> [stealth] -- have no Keywords function an alias
could simply point at.

[mouseuse] now resolves to [cursor], routing old macros through ClassicAPI's
C_Spell.CastAtCursor / C_Item.UseAtCursor. Drops the post-cast block that cast
normally and then faked a mouse click via CameraOrSelectOrMoveStart/Stop to
place the AoE circle, along with its workaround for that call spuriously
starting auto-attack.

MacroErrorChecker seeds VALID_CONDITIONALS from the alias table, so the old
names stay valid syntax without needing a placeholder ignoreKeywords entry.

MacroErrorChecker.lua

@@ -35,6 +35,14 @@ if CleveRoids.ignoreKeywords then
     end
 end
 
+-- Deprecated names still valid in macros; ParseMsg rewrites them to the current
+-- keyword, so they never reach Keywords/ignoreKeywords under their old name.
+if CleveRoids.conditionalAliases then
+    for alias, _ in pairs(CleveRoids.conditionalAliases) do
+        VALID_CONDITIONALS[alias] = true
+    end
+end
+
 -- Known valid commands
 local VALID_COMMANDS = {
     -- Core commands NOT registered via SlashCmdList (so not auto-discoverable):