feat(settings): default settings.enablePluginPadOptions to true (#7841)

This flag gates the ep_* passthrough on padoptions that shipped in 3.0.0
(PR #7698). It was introduced as opt-in, but the intent in shipping it
was to let plugins like ep_plugin_helpers' padToggle / padSelect ride
the existing broadcast/persist rail out of the box — flipping the
default closes the gap.

Why now
- ep_comments_page#422 (and sibling per-plugin reports discussed on
  Discord): stock 3.x deployments console.warn on every pad load because
  the helper detects clientVars.enablePluginPadOptions === false and
  tells the admin to flip it. With the flag default-true, the warning
  stops firing on fresh installs while still surfacing for operators
  who have explicitly opted out.
- Plugins that already depend on ep_plugin_helpers >= 0.6 expect the
  pad-wide path to work; the default-false gate silently no-op'd
  pad.changePadOption('ep_*', …) and made the helper UI inert.

Scope
- Settings.ts default flipped to true; comment rewritten to describe
  the new "operator opt-out" model rather than the old AGENTS.MD §52
  opt-in framing (that policy still applies to *new* features; this
  one has shipped and proven safe).
- settings.json.template env-var substitution default flipped to true
  so docker / supervisor configs without an explicit value get the
  new behavior.
- doc/plugins.md updated to match (default true, opt-out via
  settings.json) and the PluginCapabilities source comment.
- Backend test describe-blocks relabeled — "true" is now "(default)",
  "false" is now "(operator opt-out)". Both branches still cover the
  same matrix so the size-cap / namespace-validation paths stay
  exercised.

Compat
- Existing deployments with an explicit `"enablePluginPadOptions":
  false` in settings.json keep that value — no migration needed.
- Older clients only read clientVars.enablePluginPadOptions; the
  protocol shape is unchanged.

Closes ep_comments_page#422 (helper warning suppression for stock
deployments).

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

doc/plugins.md

@@ -267,15 +267,16 @@ below.
 ### Runtime flag
 
 The passthrough is gated by `settings.enablePluginPadOptions`, default
-`false`. Operators must opt in via `settings.json`:
+`true`. Operators who want to lock plugins out of pad-wide state can flip
+it in `settings.json`:
 
 ```json
 {
-  "enablePluginPadOptions": true
+  "enablePluginPadOptions": false
 }
 ```
 
-When enabled, the server reflects the value to every client via
+When enabled (the default), the server reflects the value to every client via
 `clientVars.enablePluginPadOptions` so plugins can detect both *capable*
 (static) and *active* (per-pad request) at the same point.
 

settings.json.template

@@ -853,11 +853,11 @@
     * accepting pad-wide values under plugin-namespaced keys matching
     * /^ep_[a-z0-9_]+$/ (e.g. ep_table_of_contents). Values are validated
     * (JSON-safe, 64 KB per key, 256 KB total) and broadcast to every
-    * connected client just like native pad-wide toggles. Disabled by
-    * default; flip to true once your plugins (e.g. ep_plugin_helpers'
-    * padToggle) require it. See doc/plugins.md.
+    * connected client just like native pad-wide toggles. Enabled by
+    * default; set to false to lock plugins out of pad-wide state. See
+    * doc/plugins.md.
     **/
-    "enablePluginPadOptions": "${ENABLE_PLUGIN_PAD_OPTIONS:false}",
+    "enablePluginPadOptions": "${ENABLE_PLUGIN_PAD_OPTIONS:true}",
 
   /*
    * Optional privacy banner shown once the pad loads. Disabled by default.

src/node/utils/PluginCapabilities.ts

@@ -12,7 +12,7 @@
 
 // True when applyPadSettings (client + server) preserves keys matching
 // /^ep_[a-z0-9_]+$/ on pad.padOptions. The runtime gate is
-// settings.enablePluginPadOptions (default false), mirrored to clients via
+// settings.enablePluginPadOptions (default true), mirrored to clients via
 // clientVars.enablePluginPadOptions. See doc/plugins.md for the full
 // contract (key namespace, validation, size caps).
 export const padOptionsPluginPassthrough = true;

src/node/utils/Settings.ts

@@ -434,11 +434,11 @@ const settings: SettingsType = {
   updateServer: "https://static.etherpad.org",
   enableDarkMode: true,
   enablePadWideSettings: true,
-  // New plugin-padOption passthrough is opt-in per AGENTS.MD §52 ("New
-  // features should be placed behind feature flags and disabled by
-  // default"). Flip to true to let plugins (e.g. ep_plugin_helpers'
-  // padToggle) ride the existing padoptions broadcast/persist rail.
-  enablePluginPadOptions: false,
+  // Lets plugins (e.g. ep_plugin_helpers' padToggle / padSelect) ride the
+  // existing padoptions broadcast/persist rail to store pad-wide options
+  // under ep_* keys. Operators who want to lock plugin-driven pad-wide
+  // state out can set this to false in settings.json.
+  enablePluginPadOptions: true,
   allowPadDeletionByAllUsers: false,
   privacyBanner: {
     enabled: false,

src/tests/backend/specs/Pad.ts

@@ -214,7 +214,7 @@ describe(__filename, function () {
     });
     afterEach(function () { console.warn = warnSpy; });
 
-    describe('with enablePluginPadOptions = true', function () {
+    describe('with enablePluginPadOptions = true (default)', function () {
       before(function () { settings.enablePluginPadOptions = true; });
 
       it('preserves ep_* keys verbatim so plugins can ride padoptions', function () {
@@ -285,10 +285,10 @@ describe(__filename, function () {
       });
     });
 
-    describe('with enablePluginPadOptions = false (default)', function () {
+    describe('with enablePluginPadOptions = false (operator opt-out)', function () {
       before(function () { settings.enablePluginPadOptions = false; });
 
-      it('drops every ep_* key — feature flag is opt-in', function () {
+      it('drops every ep_* key — operator has opted out of plugin pad-wide state', function () {
         const ps: any = Pad.Pad.normalizePadSettings({
           ep_table_of_contents: {enabled: true},
           ep_font_color: 'red',