test: extend TaskCleanupOldTasks to cover all terminal phases

[mvillmow]

Summary

• Add test cases for TASK_PHASE_ERROR, TASK_PHASE_TIMEOUT, and TASK_PHASE_CANCELLED to the TaskCleanupOldTasks E2E test
• Ensures the full terminal state set is covered by cleanup verification
• Follows up from Add failed, error, and cancelled variants to TaskStatus enum #95 by extending test coverage

Test Plan

• Formatting check passed (just format-check)
• Test file compiles cleanly
• Follows existing test patterns in distributed_grpc_test.cpp

🤖 Generated with Claude Code

[github-actions]

✅ Dependency Audit

Severity	Count
Critical	0
High	0
Medium	0
Low	0

See the Security tab for detailed findings.

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Workflow: Dependency Audit

[github-actions]

Security Scan Results

• ❌ Secret Scanning: Potential secrets found
• ✅ SAST: Completed (check Security tab for details)
• ✅ Dependency Scanning: Completed
• ✅ C++ Static Analysis: Completed
• ✅ Docker Image Scanning: 0 high, 22 medium vulnerabilities (acceptable)

Recommendations

• Review findings in the GitHub Security tab
• Check artifact uploads for detailed reports
• Address critical Docker vulnerabilities immediately

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Workflow: Security Scanning