YAML lint workflow has never used .yamllint.yaml config file

## Summary

The YAML lint workflow keeps failing.

## Timeline

| Date | Commit | Author | Change |
|------|--------|--------|--------|
| 2024-08-20 | `09b4c06` | Leon Luttenberger | Created `.yamllint.yaml` config file AND workflow. **But the workflow never used the config file** - it just ran `yamllint --format github .` |
| 2025-06-30 | `9ecd6ef` | Anton Kukushkin | Added Helm charts for strands agents demo. Changed workflow to use inline config `-d "{extends: default, ignore: ['*chart*']}"` to ignore charts. **This inadvertently made the workflow ignore `.yamllint.yaml` entirely.** |

## The Core Problem

The `.yamllint.yaml` file has always had these rules:
```yaml
rules:
line-length: disable
document-start: disable
truthy: disable
```

But **the workflow never used this config file**. It either:
1. Originally ran with default rules (no `-c` flag)
2. Later used inline config with `-d` which overrides any config file

## Questions

1. **Was the `.yamllint.yaml` file intended to be used by the workflow?** It seems like there was a disconnect - the file exists with relaxed rules, but the workflow never referenced it.

2. **Should we fix the 18 remaining lint issues or disable more rules?** After properly using the config file, there are still 18 issues (trailing spaces, missing newlines at EOF, indentation issues in `modules/sagemaker/hyperpod-eks-tf/deployspec.yaml`).

## Proposed Fix

```yaml
# .yamllint.yaml - add chart ignore (remove ignore-from-file since they can't be used together)
ignore: |
*chart*

# .github/workflows/yaml-lint.yml - use config file instead of inline config
yamllint --format github -c .yamllint.yaml .
```

This makes the workflow actually use the config file that was created for it.

## Remaining Issues After Fix

After applying the fix, 18 issues remain:

- 7 `new-line-at-end-of-file` errors
- 4 `indentation` errors (all in `modules/sagemaker/hyperpod-eks-tf/deployspec.yaml`)
- 2 `trailing-spaces` errors
- 5 `comments-indentation` warnings

These can either be fixed in the affected files or disabled in the config.

Start with .github/workflows/yaml-lint.yml and .yamllint.yaml, then run the proposed yamllint command to confirm which configuration and failures are active. Review the 18 reported issues, including modules/sagemaker/hyperpod-eks-tf/deployspec.yaml, and finish when the workflow uses the intended config and the remaining failures have been fixed or deliberately addressed in the config.

Written by the indexing model from the issue text.