fix: allow ampersand in tags to support compound tags

plugin/markdown/parser/tag.go

@@ -51,7 +51,8 @@ func isValidTagRune(r rune) bool {
 	// Underscore: word separation (snake_case)
 	// Hyphen: word separation (kebab-case)
 	// Forward slash: hierarchical tags (category/subcategory)
-	if r == '_' || r == '-' || r == '/' {
+	// Ampersand: compound tags (science&tech)
+	if r == '_' || r == '-' || r == '/' || r == '&' {
 		return true
 	}
 

plugin/markdown/parser/tag_test.go

@@ -30,6 +30,12 @@ func TestTagParser(t *testing.T) {
 			expectedTag: "work-notes",
 			shouldParse: true,
 		},
+		{
+			name:        "tag with ampersand",
+			input:       "#science&tech",
+			expectedTag: "science&tech",
+			shouldParse: true,
+		},
 		{
 			name:        "tag with underscore",
 			input:       "#2024_plans",

web/src/utils/remark-plugins/remark-tag.ts

@@ -18,7 +18,7 @@ function isTagChar(char: string): boolean {
     return true;
   }
 
-  return char === "_" || char === "-" || char === "/";
+  return char === "_" || char === "-" || char === "/" || char === "&";
 }
 
 function parseTagsFromText(text: string): Array<{ type: "text"; value: string } | { type: "tag"; value: string }> {