feat: add sf apex get invalid-classes command @W-24222796@

[WillieRuemmele]

Summary

• Add sf apex get invalid-classes command that calls the Tooling API apexCompileResults endpoint
• Returns Apex classes/triggers with compilation errors or warnings without recompiling the entire org
• Displays results in a table with name, namespace, success status, and problem details
• Supports --json output, spinner, and graceful SIGINT/SIGTERM shutdown

Work Item

@W-24222796@: add an ApexCompileResult command

Proof of Work

• Tests: 5 passing
• Lint: clean (0 errors)
• Build: clean
• Snapshot + schema: generated

Test plan

• Run sf apex get invalid-classes --target-org <org> against an org with invalid Apex classes
• Verify table output shows name, namespace, success, and problems
• Verify --json returns structured CompilationResult
• Verify spinner displays during request
• Verify clean output when no invalid classes exist