refactor: extract system prompts and add extended prompt for Opus/Haiku 4.5 (#71)

- Extract system prompts to dedicated lib/system-prompts.ts module
- Add extended system prompt (~4000 tokens) for models with higher cache minimums (Opus 4.5, Haiku 4.5)
- Clean up debug logs while preserving informational and cache-related logs
- Improve code formatting and organization in chat route

lib/utils.ts

@@ -176,6 +176,37 @@ export function replaceNodes(currentXML: string, nodes: string): string {
   }
 }
 
+/**
+ * Create a character count dictionary from a string
+ * Used for attribute-order agnostic comparison
+ */
+function charCountDict(str: string): Map<string, number> {
+  const dict = new Map<string, number>();
+  for (const char of str) {
+    dict.set(char, (dict.get(char) || 0) + 1);
+  }
+  return dict;
+}
+
+/**
+ * Compare two strings by character frequency (order-agnostic)
+ */
+function sameCharFrequency(a: string, b: string): boolean {
+  const trimmedA = a.trim();
+  const trimmedB = b.trim();
+  if (trimmedA.length !== trimmedB.length) return false;
+
+  const dictA = charCountDict(trimmedA);
+  const dictB = charCountDict(trimmedB);
+
+  if (dictA.size !== dictB.size) return false;
+
+  for (const [char, count] of dictA) {
+    if (dictB.get(char) !== count) return false;
+  }
+  return true;
+}
+
 /**
  * Replace specific parts of XML content using search and replace pairs
  * @param xmlContent - The original XML string
@@ -275,6 +306,28 @@ export function replaceXMLParts(
       }
     }
 
+    // Fourth try: character frequency match (attribute-order agnostic)
+    // This handles cases where the model generates XML with different attribute order
+    if (!matchFound) {
+      for (let i = startLineNum; i <= resultLines.length - searchLines.length; i++) {
+        let matches = true;
+
+        for (let j = 0; j < searchLines.length; j++) {
+          if (!sameCharFrequency(resultLines[i + j], searchLines[j])) {
+            matches = false;
+            break;
+          }
+        }
+
+        if (matches) {
+          matchStartLine = i;
+          matchEndLine = i + searchLines.length;
+          matchFound = true;
+          break;
+        }
+      }
+    }
+
     if (!matchFound) {
       throw new Error(`Search pattern not found in the diagram. The pattern may not exist in the current structure.`);
     }