test: fix context deletion test setup and assert config cleanup

[Syedowais312]

Summary

This PR fixes TestDeleteContext in cmd/context_test.go.

The test previously wrote to ./testdata/local.config, but cmd/testdata/ does not exist in the repository, causing go test ./cmd to fail before exercising the actual
context deletion logic.

Changes

• replace the hardcoded ./testdata/local.config path with a file under t.TempDir()
• keep the test isolated from repository-local filesystem state
• add an assertion for the last-context deletion path:
  • ReadLocalConfig() returns nil
  • the config file is removed from disk

Why

This makes the test reliable and covers the localCfg.IsEmpty() branch in deleteContext().

Verification

go test ./cmd

Previous Failure