Enable Holesail tunnels by default; keep holesail as required dep

Holesail is on unless ENABLE_HOLESAIL=0/false/off. The holesail package remains a required dependency; docs and UI copy match the new default.

test/holesail-tunnels.test.js

@@ -7,12 +7,20 @@ import {
   listTunnels,
 } from '../server/services/holesail-tunnels.js'
 
-test('isHolesailEnabled respects ENABLE_HOLESAIL', (t) => {
+test('isHolesailEnabled defaults on; ENABLE_HOLESAIL=0 disables', (t) => {
   const prev = process.env.ENABLE_HOLESAIL
+  delete process.env.ENABLE_HOLESAIL
+  t.ok(isHolesailEnabled(), 'default enabled')
   process.env.ENABLE_HOLESAIL = '1'
   t.ok(isHolesailEnabled())
+  process.env.ENABLE_HOLESAIL = 'true'
+  t.ok(isHolesailEnabled())
   process.env.ENABLE_HOLESAIL = '0'
   t.absent(isHolesailEnabled())
+  process.env.ENABLE_HOLESAIL = 'false'
+  t.absent(isHolesailEnabled())
+  process.env.ENABLE_HOLESAIL = 'off'
+  t.absent(isHolesailEnabled())
   if (prev === undefined) delete process.env.ENABLE_HOLESAIL
   else process.env.ENABLE_HOLESAIL = prev
 })
@@ -49,7 +57,7 @@ test('listTunnels starts empty', (t) => {
   t.ok(Array.isArray(listTunnels()))
 })
 
-test('createTunnel end-to-end when ENABLE_HOLESAIL=1', async (t) => {
+test('createTunnel end-to-end when holesail enabled (default)', async (t) => {
   const prev = process.env.ENABLE_HOLESAIL
   const prevPath = process.env.PEARDOCK_TUNNELS_PATH
   const fs = await import('fs')