revive schema examples

[loriab]

Summary

Restores the QCSchema example-generation and validation machinery originally introduced in #237, updated for the coexisting v1 and v2 model families.

• Adds explicit pytest --qcschema-examples generation.
• Adds separate pytest --validate-qcschema-examples validation.
• Publishes examples under v1/<Model>/ and v2/<Model>/.
• Prefixes filenames with qcelemental- and removes redundant version parameters.
• Validates examples by reparsing, exported JSON Schema, and supported convert_v() conversions.
• Adds deterministic test data and a machine-readable manifest.
• Collects examples in the Ubuntu/Python 3.13 CI lane.
• Uploads a workflow artifact and deploys it to qcschema-examples from master or testci.
• Fixes v2 JSON Schema generation for array metadata nested beneath validator wrappers.

Testing

Using py313:

• Full suite with generation: 1905 passed, 373 skipped
• Generated examples: 79 total—44 v1 and 35 v2
• Example validation: 79 passed
• Repeated generation produced an identical JSON fingerprint.
• Ordinary pytest runs leave generated examples unchanged.
• CI YAML parsing and git diff --check pass.

[codecov]

Codecov Report

❌ Patch coverage is 10.52632% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.72%. Comparing base (1391f04) to head (9ebc460).
⚠️ Report is 39 commits behind head on master.

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