fix(editor): type nested attribute expressions

packages/syntax/src/index.ts

@@ -2,6 +2,8 @@ export { Lexer, LexError, skipLiteralOrComment } from "./tokenizer.ts";
 export { formatWrn } from "./formatter.ts";
 export type { FormatWrnOptions } from "./formatter.ts";
 export { parse, parseHtmlView, ParseError, VOID_ELEMENTS } from "./parser.ts";
+export { extractInterpolations } from "./interpolation.ts";
+export type { InterpolationSegment } from "./interpolation.ts";
 export type {
   ActionBlock,
   ApiBlock,

packages/syntax/src/interpolation.ts

@@ -0,0 +1,39 @@
+export interface InterpolationSegment {
+  expression: string;
+  start: number;
+  end: number;
+}
+
+/** Extract top-level `{...}` expressions while preserving nested object/array literals. */
+export function extractInterpolations(value: string): InterpolationSegment[] {
+  const segments: InterpolationSegment[] = [];
+  let index = 0;
+  while (index < value.length) {
+    if (value[index] !== "{") {
+      index++;
+      continue;
+    }
+    const start = index++;
+    let depth = 1;
+    let quote: string | null = null;
+    while (index < value.length && depth > 0) {
+      const char = value[index]!;
+      if (quote) {
+        if (char === "\\" && index + 1 < value.length) index += 2;
+        else {
+          if (char === quote) quote = null;
+          index++;
+        }
+        continue;
+      }
+      if (char === '"' || char === "'" || char === "`") quote = char;
+      else if (char === "{") depth++;
+      else if (char === "}") depth--;
+      index++;
+    }
+    if (depth === 0) {
+      segments.push({ expression: value.slice(start + 1, index - 1).trim(), start, end: index });
+    }
+  }
+  return segments;
+}