fix: use SfError.actions (array) instead of action (string)-W-16447880

[soridalac]

Summary

• Fixed applyErrorAction in packageUtils.ts to set SfError.actions (string array) instead of err['action'] (string), which the CLI framework
  ignores
• Preserves any existing actions already set on the error before appending new ones
• Updated unit test to validate actions on the SfError object itself, not just the function return value

Test plan

• Unit tests pass (24/24) — validates actions are set as array and existing actions are preserved
• Direct library test confirms result.actions is a string[] and result.action is undefined
• E2E manual test: sf package installed list with a simulated INVALID_TYPE error renders "Try this:" in human output and "actions": [...]
  in --json output

Screenshot with --json and without --json

@W-16447880@