Per-project specialist agents instead of shared global specialists

[eltmon]

Problem

Currently there is a single shared set of specialist agents (review-agent, test-agent, merge-agent) that handle work across all projects. This causes issues:

1. Queueing conflicts - When multiple projects have work ready for review, they compete for the same review-agent
2. Context pollution - Specialists accumulate context from multiple unrelated projects
3. Scaling bottleneck - Can only process one review/test/merge at a time across all projects
4. Project-specific configuration - Different projects may need different review criteria, test commands, or merge strategies

Proposed Solution

Each project should have its own set of specialists:

~/.panopticon/specialists/
├── myn/
│   ├── review-agent/
│   ├── test-agent/
│   └── merge-agent/
├── panopticon/
│   ├── review-agent/
│   ├── test-agent/
│   └── merge-agent/
└── househunt/
    ├── review-agent/
    ├── test-agent/
    └── merge-agent/

Benefits

• Parallel processing - Multiple projects can have reviews/tests running simultaneously
• Clean context - Each specialist only knows about its project
• Custom prompts - Projects can override default specialist prompts
• Independent queues - Project A's backlog doesn't block Project B

Implementation Notes

• Specialist tmux sessions should be named specialist-<project>-<type> (e.g., specialist-myn-review-agent)
• Session IDs and history should be stored per-project
• Fallback to global specialists if project-specific ones don't exist
• Consider lazy initialization (only create specialists when first needed)

Acceptance Criteria

• Specialists are created per-project
• Specialist state (session ID, history) is stored per-project
• Multiple projects can run reviews in parallel
• Project-specific prompt overrides are supported
• Backward compatible with existing global specialists during migration