fix: yaml support & improve parser error handling experience for 'resume serve'

[karlmayer]

Fixes #665 and fixes #682

[thomasdavis]

@karlmayer thank you for the substantial work here — proper YAML support plus a better parser-error experience for resume serve was a real investment of effort. YAML handling is one of the behaviors under active review in the revived CLI, so your thinking here is directly relevant.

Here's the context: JSON Resume is under active maintenance again (2026), and resume-cli has been revived — but the codebase moved into the jsonresume.org monorepo at packages/cli (merged in jsonresume/jsonresume.org#278). This standalone repo is being archived with a redirect, so PRs against it can no longer land — which is why I'm closing this rather than merging it.

If the change still matters to you, we'd genuinely welcome a re-submission against packages/cli in the monorepo — the maintainers are active there and PRs get reviewed. Announcement: #786 · Consolidation: jsonresume/jsonresume.org#275. Thanks again for contributing during the years when this repo was quiet — it didn't go unnoticed.