Support Blizzard-style bracket groups: [a][b] Spell and [] fall-through

A clause may now carry a leading run of [group] blocks sharing one action;
groups are OR'd, first pass wins, and [] always passes. The existing
;-separated single-block form is unchanged and mixes freely.

The OR loop lives in the two single-clause evaluators, DoWithConditionals
and TestAction, which expand a multi-group clause into one-group variants
and recurse. That covers every ;-split site, /castsequence (where ; is not
a separator and the sequence is keyed by the full args), /cancelaura,
/stopmacro and the editor highlight without rewriting strings, so
action.args, the ParsedMsg/Sequences caches and highlight offsets keep
their identity.

ParseMsg scans the leading group run (quote-aware) instead of the greedy
%[(.+)%], which previously turned [a][b] into the bogus key a][b and made
such clauses fail silently on both the cast and icon paths. The flag
pattern still runs on the whole clause when there are no groups, so !Spell
is byte-identical.

TestAction reports which variant passed and TestForActiveAction stores its
conditionals, so range/usable colouring follows the passing group's @unit
rather than group 1's. /target gains ; and group support; /pfcast injects
the resolved unit into every group, not just the first. The macro checker
validates every leading block, drops the EMPTY_CONDITIONAL error, and
catches a missing action after the last group.

Extensions/MacroErrorUI.lua

@@ -697,30 +697,9 @@ local function EnsureCondHighlightPool()
     end
 end
 
--- Test whether conditionals pass for a given command + alternative text.
--- Returns: true (passes), false (fails), nil (unconditional / no conditionals)
-local function TestConditionalPasses(cmd, alternative)
-    -- Strip ? tooltip hints (irrelevant for conditional evaluation)
-    if string.find(alternative, "?", 1, true) then
-        alternative = string.gsub(alternative, "%?", "")
-    end
-
-    local hasConditional = string.find(alternative, "%[") ~= nil
-
-    -- Dynamic commands: delegate to TestAction
-    if CleveRoids.dynamicCmds[cmd] then
-        local result = CleveRoids.TestAction(cmd, alternative)
-        if not hasConditional then
-            return nil  -- unconditional
-        end
-        return result ~= nil and result ~= false
-    end
-
-    -- Non-dynamic commands: parse and evaluate Keywords manually
-    if not hasConditional then
-        return nil  -- unconditional
-    end
-
+-- Evaluate one single-group clause of a non-dynamic command against Keywords.
+-- Returns: true (passes), false (fails), nil (could not parse)
+local function EvaluateNonDynamic(alternative)
     local ok, action, conditionals = pcall(CleveRoids.GetParsedMsg, alternative)
     if not ok or not conditionals then
         return nil
@@ -745,6 +724,43 @@ local function TestConditionalPasses(cmd, alternative)
     return passes
 end
 
+-- Test whether conditionals pass for a given command + alternative text.
+-- Returns: true (passes), false (fails), nil (unconditional / no conditionals)
+local function TestConditionalPasses(cmd, alternative)
+    -- Strip ? tooltip hints (irrelevant for conditional evaluation)
+    if string.find(alternative, "?", 1, true) then
+        alternative = string.gsub(alternative, "%?", "")
+    end
+
+    local hasConditional = string.find(alternative, "%[") ~= nil
+
+    -- Dynamic commands: delegate to TestAction
+    if CleveRoids.dynamicCmds[cmd] then
+        local result = CleveRoids.TestAction(cmd, alternative)
+        if not hasConditional then
+            return nil  -- unconditional
+        end
+        return result ~= nil and result ~= false
+    end
+
+    -- Non-dynamic commands: evaluate Keywords manually. `[a][b] X` passes when
+    -- any of its groups does.
+    if not hasConditional then
+        return nil  -- unconditional
+    end
+
+    local variants = CleveRoids.ExpandBracketGroups(alternative)
+    if not variants then
+        return EvaluateNonDynamic(alternative)
+    end
+    for i = 1, variants.n do
+        if EvaluateNonDynamic(variants[i]) then
+            return true
+        end
+    end
+    return false
+end
+
 -- Find character offset ranges for each semicolon-separated alternative.
 -- Returns array of { start, finish } pairs (1-based indices within argsText).
 local function FindAlternativeOffsets(argsText)