fix: resolve OpenClaw session file lock conflicts in oc2ov tests

[kaisongli]

• Add pre-start cleanup in upgrade_openviking.sh: remove stale .lock and .jsonl.lock files, kill all residual openclaw processes before restart
• Add session lock awareness in openclaw_cli_client.py: wait for lock release before sending requests and after subprocess returns
• Optimize wait_for_sync in base_cli_test.py: enforce minimum 5s wait, check lock release before proceeding, raise poll interval to 3s minimum
• Prevent FailoverError: session file locked (timeout 10000ms) caused by concurrent access to the same session ID in CI environment

Description

Related Issue

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

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