fix(webhooks): define simplified 2026-10-07 schema

[KonstantinSerebryakov]

Current identification.scored payloads repeat detection data across signals, risk_events and flags, expose two OS mismatch keys, and lack HRE cluster references and bot owner labels. This change adopts schema 2026-10-07: one public os_mismatch, no current risk_events or fingerprint/HRE mirrors, nullable authoritative hre.*.cluster_id, and optional bot owner labels. request_id remains the scan/API join key; event_id remains the retry deduplication key. Owner identifies the provider company (for example OpenAI); agent/product attribution stays separate in client_identity.

Adds current-version constraints rejecting risk_events, fingerprint mirrors and os_mismatch2 while retaining legacy schemas. Describes nullable HRE cluster IDs and optional provider owner labels; refreshes distributed schemas and Core fixture checks.

Validation: all 74 OpenAPI tests pass, including exported schema validation and legacy fixtures. No package publishing.

Related contract changes:

• Shield.Core
• Shield.Portal.Admin
• Shield.Docs
• shieldlabs-node
• shieldlabs-go
• shieldlabs-python
• shieldlabs-php