fix(web): address model retry review feedback

packages/client/connection/src/client/fixture.ts

@@ -792,6 +792,24 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
       scenario.turn = next
       scenario.stepStarted = false
     },
+    /** Record one retry decision, then cancel its source turn before the retry starts. */
+    cancelModelRetryDuringBackoff(id: string, delayMs = 450): void {
+      const sessionId = sid(id)
+      const scenario = retryScenarios.get(sessionId)
+      if (scenario === undefined) throw new Error(`fixture: no model retry scenario for ${id}`)
+      const failure = { code: 'TRANSPORT', message: '连接被重置' }
+      append(sessionId, {
+        type: 'llm/retry',
+        data: {
+          turn: scenario.turn, step: 1,
+          provider: 'fixture', mode: 'normal', policyKey: 'fixture-normal',
+          retry: 1, maxRetries: 2, delayMs, failure,
+        },
+      })
+      append(sessionId, { type: 'turn/end', data: { turn: scenario.turn, reason: { kind: 'aborted' } } })
+      retryScenarios.delete(sessionId)
+      setRunning(sessionId, false)
+    },
     /** Finish the timing-hook retry with a finalized response in the open retry turn. */
     completeModelRetry(id: string): void {
       const sessionId = sid(id)