feat(preflight): add exploit-readiness probe and --validate-auth mode, and refresh suggested models (#476)

* feat(preflight): gate scans on an exploit-workload readiness probe

* feat: add --validate-auth to run authentication validation only

* feat: refuse reusing an auth-validation workspace for a scan

* chore: refresh suggested model IDs (Grok 4.7, OpenAI gpt-6-sol, Claude 5)

* fix(preflight): make the exploit-readiness probe trip the cyber safeguard reliably

* chore(preflight): update the exploit-readiness probe prompt

* feat: add --validate-model to run the preflight model checks only

* feat(cli): name cyber-access and app-login steps in the start loader

* feat(cli): refine start loader — skip app-login step when following, annotate preflight label

* feat(status): show Preflight and Cyber access verification rows for gated providers

* chore(preflight): suggest a fallback model in cyber-access remediation hints

* chore(preflight): drop env-var syntax from cyber-access fallback hints

* fix(preflight): separate finding heading from Target line in readiness probe

* refactor(preflight): rename exploit-readiness probe to cyber access verification

* fix(preflight): re-join finding heading with Target line in readiness probe

Reverts the heading/Target split from 22d84f2, gluing each finding's
heading back onto its Target line in the cyber-access probe's user
content.

* feat(validation): show a Checks summary in the validation log

* fix(cli): say a validation run failed, not that it could not start

* docs(ai-providers): replace broken Pi subscription link with /login steps

* feat(preflight): gate the openai-codex subscription on cyber access

.env.example

@@ -13,7 +13,7 @@ SHANNON_AI_MODEL=anthropic:claude-sonnet-4-6
 
 # --- xAI ---------------------------------------------------------------------
 # SHANNON_AI_API_KEY=your-api-key-here
-# SHANNON_AI_MODEL=xai:grok-4.5
+# SHANNON_AI_MODEL=xai:grok-4.7
 
 # --- AWS Bedrock -------------------------------------------------------------
 # Bearer token only; model must be enabled in your region.
@@ -48,9 +48,9 @@ SHANNON_AI_MODEL=anthropic:claude-sonnet-4-6
 # See the guide below to use an OpenAI subscription
 # https://github.com/KeygraphHQ/shannon/blob/main/docs/ai-providers.md#openai-codex-chatgpt-pluspro-subscription
 # SHANNON_USE_PI_AUTH=1
-# SHANNON_AI_MODEL=openai-codex:gpt-5.5
+# SHANNON_AI_MODEL=openai-codex:gpt-6-sol
 
 # Or the guide below to use an xAI subscription
 # https://github.com/KeygraphHQ/shannon/blob/main/docs/ai-providers.md#xai-grok-subscription
 # SHANNON_USE_PI_AUTH=1
-# SHANNON_AI_MODEL=xai:grok-4.6
+# SHANNON_AI_MODEL=xai:grok-4.7