fix(advisor): include scope in versioned answer-cache identity

[bearmug]

Audit baseline: aa595438650cfbaa6db310792929c6219cc003b2 (origin/main at audit start).

Problem

Advisor answer caching hashes model, question, and context inputs but omits scope, even though scope changes the generated prompt. Identical questions asked under architecture/security/etc. can return a cached answer generated for the wrong scope.

Acceptance criteria

• Include normalized scope and every prompt-affecting option in a versioned cache key.
• Different scopes miss; identical complete requests hit.
• Namespace/invalidate legacy unscoped entries.
• Add regression tests with includeRecentWork: false for deterministic isolation.