fix(client): bound nested Tool call depth

packages/client/runtime/tests/tool-call-tree.spec.ts

@@ -1,7 +1,9 @@
 import type { SessionEvent } from '@deepseek-ai/dsh-session/types'
 import { describe, expect, it } from 'vitest'
-import type { RunningToolCall } from '../src/client/sessions/conversation.ts'
-import { ToolCallTree } from '../src/client/sessions/tool-call-tree.ts'
+import type { RunningToolCall, ToolCallBlock } from '../src/client/sessions/conversation.ts'
+import {
+  MAX_TOOL_CALL_TREE_DEPTH, ToolCallTree,
+} from '../src/client/sessions/tool-call-tree.ts'
 
 const at = (seq: number, type: string, data: Record<string, unknown>): SessionEvent =>
   ({ seq, time: 1_700_000_000_000 + seq, type, data }) as unknown as SessionEvent
@@ -62,4 +64,26 @@ describe('ToolCallTree', () => {
       }],
     }])
   })
+
+  it('rejects an edge beyond the recursive depth safety limit', () => {
+    const tree = new ToolCallTree()
+    for (let depth = 1; depth < MAX_TOOL_CALL_TREE_DEPTH; depth++) {
+      tree.apply(start(depth, `call-${depth - 1}`, `call-${depth}`))
+    }
+
+    expect(tree.apply(start(
+      MAX_TOOL_CALL_TREE_DEPTH,
+      `call-${MAX_TOOL_CALL_TREE_DEPTH - 1}`,
+      `call-${MAX_TOOL_CALL_TREE_DEPTH}`,
+    ))).toBe(true)
+
+    let current: ToolCallBlock = tree.projectRunningCalls([root('call-0')])[0]!
+    let depth = 1
+    while (current.subCalls.length > 0) {
+      current = current.subCalls[0]!
+      depth++
+    }
+    expect(depth).toBe(MAX_TOOL_CALL_TREE_DEPTH)
+    expect(current.callId).toBe(`call-${MAX_TOOL_CALL_TREE_DEPTH - 1}`)
+  })
 })