fix: edit_diagram streaming and JSON repair improvements (#271)

- Add shared editDiagramOriginalXmlRef between streaming preview and tool handler
  to avoid conflicts when applying operations (fixes "cell already exists" errors)
- Add JSON repair preprocessing to fix LLM-generated malformed JSON like `:=`
- Filter out tool calls with invalid/undefined inputs from interrupted streaming
- Remove perf console logs

lib/utils.ts

@@ -743,8 +743,6 @@ function checkNestedMxCells(xml: string): string | null {
  * @returns null if valid, error message string if invalid
  */
 export function validateMxCellStructure(xml: string): string | null {
-    console.time("perf:validateMxCellStructure")
-    console.log(`perf:validateMxCellStructure XML size: ${xml.length} bytes`)
     // Size check for performance
     if (xml.length > MAX_XML_SIZE) {
         console.warn(
@@ -754,18 +752,10 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 0. First use DOM parser to catch syntax errors (most accurate)
     try {
-        console.time("perf:validate-DOMParser")
         const parser = new DOMParser()
         const doc = parser.parseFromString(xml, "text/xml")
-        console.timeEnd("perf:validate-DOMParser")
         const parseError = doc.querySelector("parsererror")
         if (parseError) {
-            const actualError = parseError.textContent || "Unknown parse error"
-            console.log(
-                "[validateMxCellStructure] DOMParser error:",
-                actualError,
-            )
-            console.timeEnd("perf:validateMxCellStructure")
             return `Invalid XML: The XML contains syntax errors (likely unescaped special characters like <, >, & in attribute values). Please escape special characters: use &lt; for <, &gt; for >, &amp; for &, &quot; for ". Regenerate the diagram with properly escaped values.`
         }
 
@@ -774,7 +764,6 @@ export function validateMxCellStructure(xml: string): string | null {
         for (const cell of allCells) {
             if (cell.parentElement?.tagName === "mxCell") {
                 const id = cell.getAttribute("id") || "unknown"
-                console.timeEnd("perf:validateMxCellStructure")
                 return `Invalid XML: Found nested mxCell (id="${id}"). Cells should be siblings, not nested inside other mxCell elements.`
             }
         }
@@ -788,16 +777,12 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 1. Check for CDATA wrapper (invalid at document root)
     if (/^\s*<!\[CDATA\[/.test(xml)) {
-        console.timeEnd("perf:validateMxCellStructure")
         return "Invalid XML: XML is wrapped in CDATA section - remove <![CDATA[ from start and ]]> from end"
     }
 
     // 2. Check for duplicate structural attributes
-    console.time("perf:checkDuplicateAttributes")
     const dupAttrError = checkDuplicateAttributes(xml)
-    console.timeEnd("perf:checkDuplicateAttributes")
     if (dupAttrError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return dupAttrError
     }
 
@@ -807,33 +792,25 @@ export function validateMxCellStructure(xml: string): string | null {
     while ((attrValMatch = attrValuePattern.exec(xml)) !== null) {
         const value = attrValMatch[1]
         if (/</.test(value) && !/&lt;/.test(value)) {
-            console.timeEnd("perf:validateMxCellStructure")
             return "Invalid XML: Unescaped < character in attribute values. Replace < with &lt;"
         }
     }
 
     // 4. Check for duplicate IDs
-    console.time("perf:checkDuplicateIds")
     const dupIdError = checkDuplicateIds(xml)
-    console.timeEnd("perf:checkDuplicateIds")
     if (dupIdError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return dupIdError
     }
 
     // 5. Check for tag mismatches
-    console.time("perf:checkTagMismatches")
     const tagMismatchError = checkTagMismatches(xml)
-    console.timeEnd("perf:checkTagMismatches")
     if (tagMismatchError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return tagMismatchError
     }
 
     // 6. Check invalid character references
     const charRefError = checkCharacterReferences(xml)
     if (charRefError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return charRefError
     }
 
@@ -842,7 +819,6 @@ export function validateMxCellStructure(xml: string): string | null {
     let commentMatch
     while ((commentMatch = commentPattern.exec(xml)) !== null) {
         if (/--/.test(commentMatch[1])) {
-            console.timeEnd("perf:validateMxCellStructure")
             return "Invalid XML: Comment contains -- (double hyphen) which is not allowed"
         }
     }
@@ -850,24 +826,20 @@ export function validateMxCellStructure(xml: string): string | null {
     // 8. Check for unescaped entity references and invalid entity names
     const entityError = checkEntityReferences(xml)
     if (entityError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return entityError
     }
 
     // 9. Check for empty id attributes on mxCell
     if (/<mxCell[^>]*\sid\s*=\s*["']\s*["'][^>]*>/g.test(xml)) {
-        console.timeEnd("perf:validateMxCellStructure")
         return "Invalid XML: Found mxCell element(s) with empty id attribute"
     }
 
     // 10. Check for nested mxCell tags
     const nestedCellError = checkNestedMxCells(xml)
     if (nestedCellError) {
-        console.timeEnd("perf:validateMxCellStructure")
         return nestedCellError
     }
 
-    console.timeEnd("perf:validateMxCellStructure")
     return null
 }