fix(sling): Set hook_bead atomically at polecat spawn time (gt-h46pk)

When slinging work to a rig (auto-spawning a polecat), the hook_bead
is now set atomically during agent bead creation rather than in a
separate updateAgentHookBead call after spawn.

This fixes cross-beads routing issues when town beads (hq-*) are slung
to rig polecats (gt-* agent beads). By setting hook_bead at creation
time within the polecat manager context, the correct beads routing is
used.

Changes:
- Add AddOptions struct with HookBead field to polecat.Manager
- Add AddWithOptions() and RecreateWithOptions() functions
- Pass HookBead through SlingSpawnOptions in cmd/polecat_spawn.go
- Pass beadID as HookBead in cmd/sling.go for rig target spawns

Note: updateAgentHookBead() is kept for non-spawn targets (existing
agents) and formula-on-bead mode (updates hook to wisp root after
creation).

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

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

internal/cmd/sling.go

@@ -238,10 +238,11 @@ func runSling(cmd *cobra.Command, args []string) error {
 				// Spawn a fresh polecat in the rig
 				fmt.Printf("Target is rig '%s', spawning fresh polecat...\n", rigName)
 				spawnOpts := SlingSpawnOptions{
-					Force:   slingForce,
-					Naked:   slingNaked,
-					Account: slingAccount,
-					Create:  slingCreate,
+					Force:    slingForce,
+					Naked:    slingNaked,
+					Account:  slingAccount,
+					Create:   slingCreate,
+					HookBead: beadID, // Set atomically at spawn time
 				}
 				spawnInfo, spawnErr := SpawnPolecatForSling(rigName, spawnOpts)
 				if spawnErr != nil {