Add doctor command for environment checks

[baily-zhang]

Motivation

Users need a read-only way to diagnose config, Docker, auth, and emulator connectivity from the CLI.

Changes

• add a new lstk doctor command with read-only config, Docker, auth, and emulator checks
• add timeout handling, per-check limits, concurrent emulator checks, and TUI support
• add unit and integration coverage for doctor success, warning, and failure scenarios

Tests

• go test ./cmd/... ./internal/...
• cd test/integration && LSTK_KEYRING=file go test -count=1 -run TestDoctor ./...

[claude]

Claude Code Review

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[gtsiolis]

Thanks for contributing, @baily-zhang! ❤️

The doctor command looks like a good first iteration.

Heads-up: The team is sorting out a contribution policy process for this repository, we will follow up here as soon as we have clarity on next steps. Thanks for your patience. ⏳

[baily-zhang]

Thanks for the update, and no worries. Glad to hear the first iteration looks useful. Happy to wait, and I’m available to make follow-up changes if needed once the process is in place.

[baily-zhang]

Btw, here's what it looks like in different scenarios