Migrate advisor onto the shared subagent runtime and add behavior coverage

[dcramer]

Objective

Validate the generic architecture by moving the existing persistent advisor onto it and covering user-visible delegation behavior.

Scope

• Represent advisor as a named, read-only agent profile.
• Remove advisor-specific message persistence after parity is proven.
• Add integration coverage for resume, result delivery, failure, and duplicate events.
• Add eval coverage for delegation, named reuse, and result consumption.

Completion

• Advisor continuity and read-only policy remain intact.
• Generic subagent storage replaces the advisor-specific session store.
• Local-agent validation covers the end-to-end workflow.