fix: Add JSON recovery for truncated streaming responses from kimi-k2 (#367)

- Add attemptJSONParse() function with recovery strategies for truncated/malformed JSON
- Handle incomplete JSON structures by closing them (}, ]}, }]}, etc.)
- Improve error handling and logging for malformed chunks
- Gracefully degrade when parsing fails instead of crashing
- Fixes issue where kimi-k2 model breaks off due to JSON truncation at newline boundaries

Author: ayorindeadunse

web/src/llm-api/openrouter.ts

@@ -1,8 +1,8 @@
-import { Agent } from 'undici'
 
 import { PROFIT_MARGIN } from '@codebuff/common/constants/limits'
 import { getErrorObject } from '@codebuff/common/util/error'
 import { env } from '@codebuff/internal/env'
+import { Agent } from 'undici'
 
 import {
   consumeCreditsForMessage,
@@ -16,12 +16,11 @@ import {
 
 import type { UsageData } from './helpers'
 import type { OpenRouterStreamChatCompletionChunk } from './type/openrouter'
-import type { InsertMessageBigqueryFn } from '@codebuff/common/types/contracts/bigquery'
-import type { Logger } from '@codebuff/common/types/contracts/logger'
 import type {
   ChatCompletionRequestBody,
-  OpenRouterErrorMetadata,
 } from './types'
+import type { InsertMessageBigqueryFn } from '@codebuff/common/types/contracts/bigquery'
+import type { Logger } from '@codebuff/common/types/contracts/logger'
 
 type StreamState = { responseText: string; reasoningText: string; ttftMs: number | null }
 
@@ -725,7 +724,7 @@ async function handleStreamChunk({
 
   if (!data.choices || !Array.isArray(data.choices) || !data.choices.length) {
     logger.debug(
-      { 
+      {
         hasChoices: 'choices' in data,
         choicesLength: Array.isArray(data.choices) ? data.choices.length : 'N/A',
         streamChunk: JSON.stringify(data).slice(0, 500),