fix(toolcall): fix deepseek function calling bug and add json repair

- Fix: Expand stream sieve keywords to support function.name: and [TOOL_CALL_HISTORY]

- Fix: Add repairInvalidJSONBackslashes to handle unescaped backslashes in Windows paths

- Sync: Update JS stream sieve to match Go implementation

- Test: Add unit tests for backslash repair and deepseek format parsing

- Tool: Move repair json test tool to tests/repair_json_tool.go

internal/js/helpers/stream-tool-sieve/sieve.js

@@ -165,19 +165,34 @@ function findToolSegmentStart(s) {
     return -1;
   }
   const lower = s.toLowerCase();
+  const keywords = ['tool_calls', 'function.name:', '[tool_call_history]'];
   let offset = 0;
   // eslint-disable-next-line no-constant-condition
   while (true) {
-    const keyIdx = lower.indexOf('tool_calls', offset);
-    if (keyIdx < 0) {
+    let bestKeyIdx = -1;
+    let matchedKeyword = '';
+
+    for (const kw of keywords) {
+      const idx = lower.indexOf(kw, offset);
+      if (idx >= 0) {
+        if (bestKeyIdx < 0 || idx < bestKeyIdx) {
+          bestKeyIdx = idx;
+          matchedKeyword = kw;
+        }
+      }
+    }
+
+    if (bestKeyIdx < 0) {
       return -1;
     }
+
+    const keyIdx = bestKeyIdx;
     const start = s.slice(0, keyIdx).lastIndexOf('{');
     const candidateStart = start >= 0 ? start : keyIdx;
     if (!insideCodeFence(s.slice(0, candidateStart))) {
       return candidateStart;
     }
-    offset = keyIdx + 'tool_calls'.length;
+    offset = keyIdx + matchedKeyword.length;
   }
 }