fix(runtime): defer invoke required flag validation

[aidandaly24]

Summary

• declare Runtime invoke --id and --payload as optional at the Commander boundary
• validate omitted required values inside the handler while preserving usage exit codes
• verify bare runtime invoke reaches the existing TUI middleware and empty payloads remain valid

Testing

• bun test src/handlers/runtime/invoke (54 pass)
• bun test (538 pass)
• bun run typecheck
• bun run lint:check
• bun run format:check
• bun run build

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.86%. Comparing base (8e2cecf) to head (2209c5c).

Additional details and impacted files

@@            Coverage Diff            @@
##           refactor    #1876   +/-   ##
=========================================
  Coverage     95.85%   95.86%           
=========================================
  Files           198      198           
  Lines          9341     9352   +11     
=========================================
+ Hits           8954     8965   +11     
  Misses          387      387           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[tejaskash]

LGTM

[Hweinstock]

I didn't realize that 2 was the standard for validation exceptions. Should we make this the default on the input validation error class? (could be a follow-up)