docs: update dataops skill and synth-data-generate prompt docs for synthetic-data-operation preflight

### Component

Documentation

### Bug Description

Recent changes (dataops SKILL.md and the synth-data-generate prompt) introduced a mandatory `SYNTHETIC_DATA_OPERATION_V1` preflight gate, a new synthetic-data-operation-contract reference, and a new JSON schema for validating preflight records. `docs/reference/skills/data-science-engineering/dataops.md` and `docs/reference/prompts/data-science-engineering/synth-data-generate.md` do not describe this preflight gate, the `validate`/`commit-local` commands, or the new synthetic-data-operation-contract reference at all, so the published reference pages no longer reflect what the skill/prompt actually require.

### Expected Behavior

- `docs/reference/skills/data-science-engineering/dataops.md` should mention the synthetic-data-operation-contract reference and preflight/validate/commit-local workflow in its "When to use it" and/or "Example usage" sections.
- `docs/reference/prompts/data-science-engineering/synth-data-generate.md` should describe the mandatory Step 0 preflight validation (require a current approved `SYNTHETIC_DATA_OPERATION_V1` record before project creation, source access, or data generation) in its "How to use it" section.
- Run `npm run docs:generate` after updating the auto-generated overview blocks, and update the manual "When to use it"/"How to use it" sections by hand per docs contribution conventions.

### Steps to Reproduce

1. Compare `.github/skills/data-science-engineering/dataops/SKILL.md` (commit a57047f0, "feat(dataops): enforce synthetic data lineage and fairness") against `docs/reference/skills/data-science-engineering/dataops.md`.
2. Compare `.github/prompts/data-science-engineering/synth-data-generate.prompt.md` Step 0 against `docs/reference/prompts/data-science-engineering/synth-data-generate.md`.

### Additional Context

Source files:
- `.github/skills/data-science-engineering/dataops/SKILL.md`
- `.github/skills/data-science-engineering/dataops/references/synthetic-data-operation-contract.md`
- `.github/prompts/data-science-engineering/synth-data-generate.prompt.md`

Documentation files needing updates:
- `docs/reference/skills/data-science-engineering/dataops.md`
- `docs/reference/prompts/data-science-engineering/synth-data-generate.md`

> Generated by [Documentation Update Check](https://github.com/microsoft/hve-core/actions/runs/34512278181) · auto · 44.2 AIC · ⌖ 1.87 AIC · ⊞ 10K · [◷](https://github.com/search?q=repo%3Amicrosoft%2Fhve-core+is%3Aissue+%22gh-aw-workflow-call-id%3A+microsoft%2Fhve-core%2Fdoc-update-check%22&type=issues)

Compare .github/skills/data-science-engineering/dataops/SKILL.md and its synthetic-data-operation-contract.md reference with docs/reference/skills/data-science-engineering/dataops.md. Compare the prompt's Step 0 with docs/reference/prompts/data-science-engineering/synth-data-generate.md, then update the specified manual sections and run npm run docs:generate for overview blocks. Done means both published pages describe the mandatory preflight and validate/commit-local workflow.

Written by the indexing model from the issue text.