fix(e2b): reject incomplete process streams without exit code

[guslegend0510]

PR 描述

AgentScope-Java Version

2.0.3-SNAPSHOT

Description

Fixes #2824.

E2bEnvdProcessClient.drainStartStream() previously returned Integer.MIN_VALUE when the envd response stream ended before a process exit event was received.

The sentinel was then interpreted as a real non-zero process exit code, causing an incomplete transport response to be misreported as a command failure.

This change:

• Removes the Integer.MIN_VALUE fallback.
• Throws an explicit IOException when the stream ends without a process exit code.
• Preserves valid zero and non-zero exit codes.
• Adds regression coverage for EOF, truncated frame length, and truncated frame payload scenarios.

The missing exit code is treated as an incomplete transport response rather than being assumed to mean success.

Tests

Targeted tests:

mvn -pl agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-e2b \
  -am \
  -Dtest=E2bEnvdProcessClientTest \
  -Dsurefire.failIfNoSpecifiedTests=false \
  test

Result: 10 tests passed.

Full module tests:

mvn -pl agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-e2b \
  -am test

Results:

• agentscope-core: 2294 tests, 0 failures
• agentscope-harness: 834 tests, 0 failures
• agentscope-extensions-sandbox-e2b: 14 tests, 0 failures

Checklist

• Code is formatted with Spotless
• Targeted and module tests pass
• No public API changes
• Ready for review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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