fix: ensure tests never access ~/.km directory

[dluc]

Summary

• Tests now create isolated temporary directories instead of using ~/.km
• Enforces proper test isolation as required by docs/AGENTS.md
• Prevents tests from touching user data

Changes

• tests/Main.Tests/Unit/CLI/CliApplicationBuilderTests.cs:

  • Implemented IDisposable for proper cleanup
  • Uses temp directory with unique GUID for each test
  • Passes --config <temp_path> to avoid ~/.km access

• tests/Main.Tests/Integration/ExamplesCommandOutputTest.cs:

  • Creates isolated temp directory for config file
  • Cleans up temp directory in finally block

Test plan

• All 520 tests pass (306 Core + 214 Main)
• Zero skipped tests
• Code coverage at 83.82% (above 80% threshold)
• build.sh passes with 0 warnings
• format.sh passes
• coverage.sh passes
• Tests no longer access ~/.km directory

Compliance

Per docs/AGENTS.md:

"Tests must never read or write files at ~/.km/ - Tests must use temp dirs"