fix: skip streaming normalization on finish_reason length

Truncated tool calls (finish_reason: 'length') now preserve the raw
buffer instead of normalizing into executable commands, preventing
incomplete commands from becoming runnable.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/api/openaiShim.test.ts

@@ -1420,7 +1420,7 @@ test('does not normalize incomplete streamed Bash commands when finish_reason is
     .map(event => (event.delta as Record<string, unknown>).partial_json)
     .join('')
 
-  expect(streamedInput).toBe('{"command":"rg --fi"}')
+  expect(streamedInput).toBe('rg --fi')
 })
 
 test('does not repair truncated Bash objects that do not contain command', async () => {

src/services/api/openaiShim.ts

@@ -692,10 +692,15 @@ async function* openaiStreamToAnthropic(
           // Close active tool calls
           for (const [, tc] of activeToolCalls) {
             if (tc.normalizeAtStop) {
+              let partialJson: string
+              if (choice.finish_reason === 'length') {
+                // Truncated by max tokens — preserve raw buffer to avoid
+                // turning an incomplete tool call into an executable command
+                partialJson = tc.jsonBuffer
+              } else {
                 const repairedStructuredJson = repairPossiblyTruncatedObjectJson(
                   tc.jsonBuffer,
                 )
-              let partialJson: string
                 if (repairedStructuredJson) {
                   partialJson = repairedStructuredJson
                 } else {
@@ -703,6 +708,7 @@ async function* openaiStreamToAnthropic(
                     normalizeToolArguments(tc.name, tc.jsonBuffer),
                   )
                 }
+              }
 
               yield {
                 type: 'content_block_delta',