Remove keepalive file infrastructure for feed-based wake model (gt-vdprb.2)

- Remove TouchTownActivity() calls from root.go PersistentPreRun hook
- Remove ReadTownActivity() and activity-based backoff from daemon.go
- Delete TouchTownActivity/ReadTownActivity functions from keepalive.go
- Replace dynamic backoff with fixed 10-min recovery heartbeat

Normal wake is now handled by feed subscription (bd activity --follow).
The daemon is a safety net for dead sessions, GUPP violations, and orphaned work.

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

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

internal/keepalive/keepalive.go

@@ -75,69 +75,6 @@ func TouchInWorkspace(workspaceRoot, command string) {
 	_ = os.WriteFile(keepalivePath, data, 0644) // non-fatal: status file for debugging
 }
 
-// TouchTownActivity writes a town-level activity signal to ~/gt/daemon/activity.json.
-// This is used by the daemon to implement exponential backoff when the town is idle.
-// Any gt command activity resets the backoff to the base heartbeat interval.
-// It silently ignores errors (best-effort signaling).
-func TouchTownActivity(command string) {
-	// Get town root from GT_TOWN_ROOT or default to ~/gt
-	townRoot := os.Getenv("GT_TOWN_ROOT")
-	if townRoot == "" {
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return
-		}
-		townRoot = filepath.Join(home, "gt")
-	}
-
-	daemonDir := filepath.Join(townRoot, "daemon")
-
-	// Ensure daemon directory exists
-	if err := os.MkdirAll(daemonDir, 0755); err != nil {
-		return
-	}
-
-	state := State{
-		LastCommand: command,
-		Timestamp:   time.Now().UTC(),
-	}
-
-	data, err := json.Marshal(state)
-	if err != nil {
-		return
-	}
-
-	activityPath := filepath.Join(daemonDir, "activity.json")
-	_ = os.WriteFile(activityPath, data, 0644) // non-fatal: activity signal for daemon
-}
-
-// ReadTownActivity returns the current town-level activity state.
-// Returns nil if the file doesn't exist or can't be read.
-func ReadTownActivity() *State {
-	townRoot := os.Getenv("GT_TOWN_ROOT")
-	if townRoot == "" {
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return nil
-		}
-		townRoot = filepath.Join(home, "gt")
-	}
-
-	activityPath := filepath.Join(townRoot, "daemon", "activity.json")
-
-	data, err := os.ReadFile(activityPath)
-	if err != nil {
-		return nil
-	}
-
-	var state State
-	if err := json.Unmarshal(data, &state); err != nil {
-		return nil
-	}
-
-	return &state
-}
-
 // Read returns the current keepalive state for the workspace.
 // Returns nil if the file doesn't exist or can't be read.
 func Read(workspaceRoot string) *State {