Instrument gt commands to emit events to activity feed (gt-7aw1m)

Add events.LogFeed calls to the following gt commands:
- nudge.go: Log TypeNudge events when nudging agents
- unsling.go: Log TypeUnhook events when removing work from hooks
- up.go: Log TypeBoot events when starting Gas Town services
- down.go: Log TypeHalt events when stopping Gas Town services
- stop.go: Log TypeKill events when stopping polecat sessions
- polecat_spawn.go: Log TypeSpawn events when spawning polecats

Also add helper functions to events package:
- UnhookPayload: Creates payload for unhook events
- KillPayload: Creates payload for kill events
- HaltPayload: Creates payload for halt events

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

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

internal/cmd/polecat_spawn.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/steveyegge/gastown/internal/config"
 	"github.com/steveyegge/gastown/internal/constants"
+	"github.com/steveyegge/gastown/internal/events"
 	"github.com/steveyegge/gastown/internal/git"
 	"github.com/steveyegge/gastown/internal/polecat"
 	"github.com/steveyegge/gastown/internal/rig"
@@ -161,6 +162,9 @@ func SpawnPolecatForSling(rigName string, opts SlingSpawnOptions) (*SpawnedPolec
 
 	fmt.Printf("%s Polecat %s spawned\n", style.Bold.Render("✓"), polecatName)
 
+	// Log spawn event to activity feed
+	_ = events.LogFeed(events.TypeSpawn, "gt", events.SpawnPayload(rigName, polecatName))
+
 	return &SpawnedPolecatInfo{
 		RigName:     rigName,
 		PolecatName: polecatName,