Accept more question-mark reactions as explain triggers

Now triggers on ❓ ❔ ⁉ ⁉️ 🤔 ? ？ — covers the obvious red/white/thinking
variants, the exclamation-question combo (with and without VS16), and
plain ascii / fullwidth question marks for keyboard users.

internal/explainer/explainer.go

@@ -19,9 +19,23 @@ import (
 	"maunium.net/go/mautrix/id"
 )
 
-// QuestionEmoji is the reaction key that triggers a summary. Matrix delivers
-// the reaction key verbatim — Element sends "❓" (U+2753).
-const QuestionEmoji = "❓"
+// questionReactions is the set of reaction keys that trigger a summary.
+// Matrix delivers the key verbatim; we accept several question-y glyphs plus
+// plain "?" so users don't have to hunt for the exact red question mark.
+var questionReactions = map[string]bool{
+	"❓":  true, // U+2753 red question mark
+	"❔":  true, // U+2754 white question mark
+	"⁉":  true, // U+2049 exclamation question mark
+	"⁉️": true, // U+2049 + VS16 (emoji presentation)
+	"🤔":  true, // U+1F914 thinking face
+	"?":  true, // plain ascii
+	"？":  true, // U+FF1F fullwidth question mark
+}
+
+// IsQuestionReaction reports whether a reaction key should trigger a summary.
+func IsQuestionReaction(key string) bool {
+	return questionReactions[key]
+}
 
 // cooldown for repeat-explain on the same story (per process).
 const explainCooldown = 5 * time.Minute
@@ -47,7 +61,7 @@ func New(mx *matrix.Client, ollama *classifier.OllamaClient) *Explainer {
 // Handle is the entry point used as a callback from poster.HandleReaction.
 // It runs synchronously — callers should invoke it in a goroutine.
 func (e *Explainer) Handle(roomID id.RoomID, rootEventID id.EventID, guid, channel, emoji string) {
-	if emoji != QuestionEmoji {
+	if !IsQuestionReaction(emoji) {
 		return
 	}
 	if !e.acquire(guid) {