fix(plugins): close LA5 ownership races

docs/plans/2026-08-14-launcher-campaign.md

@@ -155,7 +155,11 @@ Field rules:
   for gui/guiSelect/probe.
 - `credential`: always `{ "provider": "standardInput", "reference":
   "session" }` for launcher-composed configs.
-- `plugins`/`loginCommands`/`loginCommandDelayMs`/`statusFile`: optional,
+- `plugins`: absent/null means load all discovered plugins (preserving the
+  developer flow); explicit `[]` means load none. Launcher-composed
+  normal-empty and probe sessions emit `[]` so they cannot load arbitrary
+  machine-local plugins.
+- `loginCommands`/`loginCommandDelayMs`/`statusFile`: optional,
   omitted-when-unset (never null, never `[]` for empty). Absent
   `loginCommandDelayMs` means 500.
 
@@ -297,7 +301,9 @@ are backed by Core-owned types already; only `Ui` (`BufferedUiRegistry`) is
 genuinely App-only. Headless has zero plugin hosting today (confirmed).
 
 1. Session-config `Plugins` allow-list filters the discovery result on BOTH
-   hosts (absent list = load all, preserving today's dev behavior).
+   hosts (absent/null list = load all, preserving today's dev behavior;
+   explicit `[]` = load none). Launcher-composed normal-empty and probe
+   sessions emit `[]`.
 2. `HeadlessPluginHost : IPluginHost` in Headless over the same Core-owned
    `State`/`Events`/`Selection`; `Ui` is an explicit no-op behind a new
    capability flag on `IPluginHost` (e.g. `HasUi`) so plugins can detect

docs/superpowers/specs/2026-08-14-launcher-campaign-design.md

@@ -168,7 +168,9 @@ Hand-editability is a property of the format, not a required workflow.
 `HeadlessConfiguration` shape extended with:
 
 - `Plugins: string[]` — plugin names to load from the standard
-  `PluginsDirectory`; hosts load exactly this set.
+  `PluginsDirectory`; absent/null loads all discovered plugins, while an
+  explicit empty array loads none. Launcher-composed normal-empty and probe
+  sessions emit the empty array.
 - `LoginCommands: string[]` — ordered chat-typed strings.
 - Graphical host: `Character` selector may be ABSENT → character-select
   screen instead of auto-enter.