user provisioning: the platform pushes the account list to plugins that declare it

a plugin that creates accounts in an upstream service — jellyfin first, immich
next — needs to know who the platform's users are. it now gets told.

DECLARED IN THE MANIFEST, not asserted at registration. `name` and `handles`
arrive on an unauthenticated socket and are believed, so a capability claimed
there would be a plugin granting itself one. the manifest was reviewed when the
owner installed it, and sits beside `permissions` where "this plugin will be
told who your users are" belongs — on the install screen, not discovered later.

PUSHED, not requested. a sidecar has no authenticated way to ask, so a request
could only be answered, never authorised. a push inverts that: the platform
decides who gets it, and a caller registering under a name with no such
manifest gets nothing.

`listProvisionableUsers` is a hand-written projection — id, email, username,
name, role — and NOT `select *`. `users` holds `password` and `os_user`, and
`getUsers()` returns both, so a plugin reaching for the obvious function would
get every account's password hash. naming the columns means adding a secret to
the table cannot silently add it to what plugins receive. pinned by a test that
asserts the key set, not just the absence of today's secrets.

the owner is excluded. they bypass every permission check and already have
whatever upstream account they want; provisioning them is at best a no-op and
at worst a second admin nobody asked for.

sent after the ack rather than inside it, so registration never waits on a
database query — a slow postgres would otherwise stall every sidecar's startup,
and none of them need the list to start.

and re-sent on every account create and delete, because the registration copy
is a snapshot: a plugin still holding a deleted user would keep an upstream
login alive for someone the platform has removed. read once per broadcast, so
two plugins cannot be told different things about the same moment.

src/servers/plugins/manifest.ts

@@ -263,6 +263,21 @@ export type PluginManifest = {
    * See `npm-deps.ts`.
    */
   npmDependencies?: Record<string, string>;
+
+  /**
+   * This plugin creates accounts in its upstream service, one per Officer account.
+   *
+   * Declared HERE rather than asserted at registration, so it is reviewed when the owner installs the
+   * plugin and shown beside the permissions — "this plugin will be told who your users are" is exactly
+   * the sort of thing a person wants on the install screen rather than discovered afterwards.
+   *
+   * What it buys the plugin: on registering, its sidecar is sent the account list — id, email, username,
+   * name, role, owner excluded. See `listProvisionableUsers`, which is a hand-written projection so a
+   * password hash cannot reach a plugin by accident.
+   *
+   * See plugins/USER_PROVISIONING.md for what a plugin is then expected to do with it.
+   */
+  userProvisioning?: boolean;
 };
 
 /** What the platform knows about a plugin on disk: its manifest, plus everything the tree said. */