feat(v1.1.8): users::* SDK module + register hook

Rhai bridge for the v1.1.8 users::* namespace, wired through
sdk::register_all. Collection-less surface (mirrors email::/secrets::,
not kv::'s handle pattern) — app_id never appears on the script-side
signature; the service derives it from cx.app_id.

Eighteen functions bound:

  * CRUD: users::create / get / find_by_email / update / delete / list
  * Auth: users::login (returns session token string or ()),
          users::verify (returns user map or ()),
          users::logout
  * Email-tied: users::send_verification_email / verify_email /
          request_password_reset / complete_password_reset /
          invite / accept_invite (two arities: with/without
          display_name override)
  * Roles: users::add_role / remove_role / has_role

Bindings for methods whose service impl isn't in place yet (email
flows, roles, invitations) still route to the trait — the service
returns UsersError::Backend("not yet implemented") which surfaces
as a Rhai runtime error. Later v1.1.8 commits replace the service
stubs without re-touching the bridge.

User map shape: id, email, display_name, email_verified_at,
last_login_at, created_at (rfc3339), updated_at (rfc3339), roles (Vec).
Never password_hash. list returns #{ users: [...], next_cursor }
where next_cursor is the rfc3339 timestamp of the last row.

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

crates/executor-core/src/sdk/mod.rs

@@ -22,6 +22,7 @@ pub mod kv;
 pub mod pubsub;
 pub mod secrets;
 pub mod stdlib;
+pub mod users;
 
 pub use bridge::{dynamic_to_json, json_to_dynamic};
 pub use cx::SdkCallCx;
@@ -45,5 +46,6 @@ pub fn register_all(engine: &mut RhaiEngine, services: &Services, cx: Arc<SdkCal
     files::register(engine, services, cx.clone());
     pubsub::register(engine, services, cx.clone());
     secrets::register(engine, services, cx.clone());
-    email::register(engine, services, cx);
+    email::register(engine, services, cx.clone());
+    users::register(engine, services, cx);
 }