fix: preserve sitelinks update payload shape

[Adel7418]

Summary

• fix live sitelinks.update payload shape for UTM apply quick links after Yandex error_code=55
• request full SitelinksSet top-level fields (Id, Name, Status, Type) from sitelinks.get
• preserve the full SitelinksSet when changing only Href values, and fail closed before update if live read response is incomplete
• add regression coverage for full-shape preservation, missing-field fail-closed behavior, and sitelinks_get FieldNames

Safety

• no live Yandex writes performed
• live write path remains gated by existing approved/idempotency/dry_run controls
• provider errors / incomplete readbacks still fail closed without false applied=true

Verification

• Evidence PASS: /home/flora/directpilot-beta/.hermes/evidence/20260626-020015-fix-sitelinks-update-error55-final
• Verifier PASS
• Reviewer PASS
• uv run pytest tests/test_utm_sitelinks_apply.py tests/test_utm_endpoints.py -q — 35 passed
• uv run pytest -q — 593 passed
• uv run python scripts/check_openapi_sync.py — PASS
• uv run python scripts/check_no_secrets_in_git.py — PASS