Fix: handle connection errors gracefully and add comprehensive tests

[utkarsh232005]

Fixes #12. This PR introduces graceful error handling when Kubernetes or Docker APIs are unreachable, adds unit tests for all commands, sets up a CI workflow, and adds an interactive 'kdm config setup' command for notification services using @vr_patel/tui.

[Copilot]

Pull request overview

This PR addresses issue #12 where kdm show runners crashed on Kubernetes connection errors. It wraps the show commands in try/catch and uses Promise.allSettled so a failure in one backend (Docker or Kubernetes) no longer aborts the whole command. It also adds Vitest-based unit tests for several commands and a CI workflow to run them on PRs.

Changes:

• Graceful error handling in showContainers, showPods, and showRunners (using Promise.allSettled), plus safer error-message extraction in the Docker/Kubernetes fetchers.
• New Vitest unit tests for show, watch, logs, health, and config commands.
• New GitHub Actions workflow that runs npm test on PRs against main/master using Node 20.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/commands/show.ts	Exports show subcommands and adds try/catch + Promise.allSettled for graceful failure handling.
src/docker/containers.ts	Uses safer instanceof Error check when formatting the error message.
src/kubernetes/pods.ts	Same safer error-message extraction as Docker side.
src/tests/show.test.ts	Tests that showRunners/showPods handle backend failures without crashing.
src/tests/watch.test.ts	Tests that the watch command registers and clears the screen / renders dashboard.
src/tests/logs.test.ts	Tests logs command registration and logger.info invocation.
src/tests/health.test.ts	Tests health command registration and logger.info invocation.
src/tests/config.test.ts	Tests config set/list/clear subcommands including integer parsing for alert_cooldown.
.github/workflows/test.yml	Adds CI workflow to run npm test with Node 20 on PRs to main/master.

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