Report all validation errors instead of stopping at first failure

[eshaffer321]

what's this about

Right now if you validate a bunch of files and one fails, you have to fix it and run again to find the next error. Rinse and repeat until all issues are found. Kind of annoying in CI.

This PR makes the validator check all files before exiting, so you see every problem in one go.

Before:

$ validate-entity file1.yaml file2.yaml file3.yaml
Failed to validate file1.yaml: Invalid schema
# stops here, never checks the other files

After:

$ validate-entity file1.yaml file2.yaml file3.yaml

============================================================
Validation Summary:
  Total files: 3
  ✓ Passed: 1
  ✗ Failed: 2
============================================================

Failed files:
  ✗ file1.yaml
    Invalid schema
  ✗ file3.yaml
    Missing required field

what changed

• validate() now collects errors and keeps going instead of bailing early
• added a summary at the end (total/passed/failed)
• verbose mode shows the full error list
• quiet mode still shows inline errors plus the summary
• exit codes stay the same (0 = all good, 1 = something failed)
• github actions mode calls setFailed once with all the errors

testing

added tests for multi-file validation, summary output, and verbose/quiet modes. all existing tests still pass.

backwards compat

exit codes unchanged. output is additive - you just get more info now.

[punkle]

@eshaffer321 this is a great idea. It looks like my recent updates/changes have caused some conflicts unfortunately.

[eshaffer321]

@punkle fixed the merge conflicts

[punkle]

@eshaffer321 I believe we need to increment the version in the package.json in order for it to be properly released when it is merged. Could you do that. I think we can call this minor.