fix: remove vestigial state.json files from agent directories

Agent directories (witness/, refinery/, mayor/) contained state.json files
with last_active timestamps that were never updated, making them stale and
misleading. This change removes:

- initAgentStates function that created vestigial state.json files
- AgentState type and related Load/Save functions from config package
- MayorStateValidCheck from doctor checks
- requesting_* lifecycle verification (dead code - flags were never set)
- FileStateJSON constant and MayorStatePath function

Kept intact:
- daemon/state.json (actively used for daemon runtime state)
- crew/<name>/state.json (operational CrewWorker metadata)
- Agent state tracking via beads (the ZFC-compliant approach)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/doctor.go

@@ -30,7 +30,6 @@ Workspace checks:
   - rigs-registry-exists     Check mayor/rigs.json exists (fixable)
   - rigs-registry-valid      Check registered rigs exist (fixable)
   - mayor-exists             Check mayor/ directory structure
-  - mayor-state-valid        Check mayor/state.json is valid (fixable)
 
 Infrastructure checks:
   - daemon                   Check if daemon is running (fixable)