Simplify Inference Provider output + add --verbose flag + Redpill attestation

Step [4/5] output is now a clean 3-line summary by default:
  Confidential AI:      Verified in TEE
  PrivateClaw Gateway:  Verified in TEE
  Status:               PASS

The full diagnostic (endpoint, VCEK cert chain details, platform, tee-proxy
info) moves behind `privateclaw verify --verbose` / `-v`. All existing
cryptographic verification logic is preserved — only the display changes.

When the gateway falls over to Redpill, we now actually verify Redpill's
attestation endpoint (https://api.redpill.ai/v1/attestation/report) by
checking it returns valid JSON with signing_address, intel_quote, and
nvidia_payload fields. Deep Intel TDX + NVIDIA RAS verification is deferred
(noted in --verbose output).

Status rollup:
  - Confidential AI verified + Gateway verified -> PASS
  - Redpill verified + Gateway verified + failover active -> WARN
  - Any sub-check failed -> FAIL

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Dobby