controller v0.67.0: intermediary-mount — HDD_PATH repoint + drive-absent gate + H1 routes

Drives are visible in-guest only at the STABLE /mnt/felhom-drives/<name>; the
registered path + HDD_PATH + FileBrowser source repoint there while agent calls
map back to raw /mnt/<name> (agentWhere). Enroll binds-under-parent before
register. Drive-absent GATE (planDriveGates + 30s driveGateLoop) stops/blocks
apps when a drive vanishes and auto-restarts on return; start-gate refuses start
when the drive is absent. H1 endpoints (disconnect/reconnect/restart-apps) routed
onto host-side ops. Non-hollow tests + companions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

controller/internal/web/server.go

@@ -104,6 +104,10 @@ func NewServer(cfg *config.Config, stackMgr *stacks.Manager, cpuCollector *syste
 
 	s.loadTemplates()
 	go s.cleanupSessions()
+	// Drive-absent gate reconcile (intermediary-mount model): the periodic absent/return detector that
+	// replaced the retired slice-8C watchdog. Stops+blocks apps whose drive vanished, auto-restarts them
+	// when it returns. No-op when the agent is unreachable.
+	go s.driveGateLoop()
 
 	// Log auth source on startup
 	if sett != nil && sett.GetPasswordHash() != "" {