fix: gt unsling now correctly clears hooks for remote agents (gt-yea94)

The unsling command had two bugs:
1. It used the local beads directory instead of the target agent's rig
2. It looked for status=hooked beads instead of the agent bead's hook_bead field

Changes:
- unsling.go: Rewrote to use agent bead's hook_bead field (matches how sling works)
- unsling.go: Now uses target agent's rig beads path, not local
- status.go: Prefer SQLite columns (issue.HookBead, issue.AgentState) over
  parsing description text, with fallback for legacy beads
- beads.go: Added AgentState field to Issue struct for SQLite column access

This fixes the issue where `gt unsling gastown/crew/joe` would say "no work hooked"
even when gt status showed joe had a hook.

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

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

internal/beads/beads.go

@@ -103,8 +103,9 @@ type Issue struct {
 	Labels      []string `json:"labels,omitempty"`
 
 	// Agent bead slots (type=agent only)
-	HookBead string `json:"hook_bead,omitempty"` // Current work attached to agent's hook
-	RoleBead string `json:"role_bead,omitempty"` // Role definition bead (shared)
+	HookBead   string `json:"hook_bead,omitempty"`   // Current work attached to agent's hook
+	RoleBead   string `json:"role_bead,omitempty"`   // Role definition bead (shared)
+	AgentState string `json:"agent_state,omitempty"` // Agent lifecycle state (spawning, working, done, stuck)
 
 	// Counts from list output
 	DependencyCount int `json:"dependency_count,omitempty"`