fix(sling): auto-attach work molecule and handle dead polecats

Combines three related sling improvements:

1. Auto-attach mol-polecat-work (Issue #288)
   - Automatically attach work molecule when slinging to polecats
   - Ensures polecats have standard guidance molecule attached

2. Fix polecat hook with molecule (Issue #197)
   - Use beads.ResolveHookDir() for correct directory resolution
   - Prevents bd cook from failing in polecat worktree

3. Spawn fresh polecat when target has no session
   - When slinging to a dead polecat, spawn fresh one instead of failing
   - Fixes stale convoys not progressing due to done polecats

internal/cmd/sling_batch.go

@@ -111,6 +111,11 @@ func runBatchSling(beadIDs []string, rigName string, townBeadsDir string) error
 		// Update agent bead state
 		updateAgentHookBead(targetAgent, beadID, hookWorkDir, townBeadsDir)
 
+		// Auto-attach mol-polecat-work molecule to polecat agent bead
+		if err := attachPolecatWorkMolecule(targetAgent, hookWorkDir, townRoot); err != nil {
+			fmt.Printf("  %s Could not attach work molecule: %v\n", style.Dim.Render("Warning:"), err)
+		}
+
 		// Store args if provided
 		if slingArgs != "" {
 			if err := storeArgsInBead(beadID, slingArgs); err != nil {