Optimize test performance: consolidate credentials tests

[gricha]

Summary

• Consolidates credentials.test.ts from 4 separate describe blocks (each with its own agent) to 1 describe block with a shared agent
• Each agent startup takes ~3s, so this saves ~9s of agent startup time
• The test file went from 53s → 22s locally (~30s savings)

Background

The test CI job was taking ~6 minutes. Investigation showed:

• Tests run sequentially (parallelization causes race conditions due to Docker resource contention)
• The slowest tests are integration tests that create Docker containers (~8s per container)
• credentials.test.ts was particularly inefficient with 4 separate agents

Impact

• Local test time: ~170s (no change to total, but credentials tests now 22s vs 53s)
• Expected CI improvement: ~30s off the test job

Future optimizations considered (but deferred):

• Test parallelization (causes failures due to Docker conflicts)
• Workspace reuse in cli.test.ts (risky - tests explicitly test create/delete)
• Pre-warmed container pools (requires infrastructure changes)

Test plan

• All 101 tests pass locally
• CI tests pass and show improved timing

🤖 Generated with Claude Code