fix: TeamManager admin rules, close role self-escalation, escalate-only resync (#27)

TeamManager could not manage the roster: updateRule allowed self-update
only and deleteRule was superuser-only. The same self-update rule also
left a privilege escalation open — it did not restrict fields, so any
authenticated user could PATCH their own role to "admin".

- team_members rules (migration 1781000003 + base migration + setup
  script mirror):
    update: (@request.auth.id = id && @request.body.role:isset = false)
            || @request.auth.role = "admin"
    delete: @request.auth.role = "admin"
  Self-service onboarding keeps working (it never touches role); the
  role field is admin-only; deletion is admin-only.
- pb_hooks/team_members.pb.js: the ENTRA_ADMIN_EMAILS resync is now
  escalate-only — it guarantees admin for allow-list members on every
  login but no longer demotes, otherwise every TeamManager promotion
  would revert on the member's next sign-in (ADR-004 amended).
- TeamManager.jsx: info text updated to the new behaviour.

Verified with a two-identity mock-OIDC matrix (11/11): allow-list vs
regular login, self-escalation blocked while onboarding self-update
still works, cross-user update/delete blocked, admin promote/demote/
delete work, promotion survives the member's next login, allow-list
admin stays admin. Regression: #22 matrix 9/9, #24 matrix 8/8, #18
harness 15/15, npm test 112/112, eslint clean.

Closes #27

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pb_migrations/1781000003_team_members_admin_rules.js

@@ -0,0 +1,52 @@
+/// <reference path="../pb_data/types.d.ts" />
+//
+// Issue #27 — TeamManager roster management + close role self-escalation.
+//
+// The collection shipped with `updateRule: '@request.auth.id = id'` and
+// `deleteRule: null`. That broke the TeamManager admin panel (admins could
+// not change roles or remove members) AND left a privilege escalation open:
+// the self-update rule did not restrict fields, so any authenticated user
+// could PATCH their own `role` to "admin".
+//
+// New rules:
+//   update — a user may update their own record but NOT the `role` field
+//            (onboarding only touches enrollment fields); admins may update
+//            anyone, including `role`.
+//   delete — admins only.
+//
+// Environments that have not applied 1781000000 yet get these rules directly
+// from that (updated) migration; this follow-up exists for databases where it
+// already ran (Labs). Applying both is harmless (same values).
+const UPDATE_RULE = '(@request.auth.id = id && @request.body.role:isset = false) || @request.auth.role = "admin"';
+const DELETE_RULE = '@request.auth.role = "admin"';
+
+migrate((app) => {
+  let col;
+  try {
+    col = app.findCollectionByNameOrId("team_members");
+  } catch (_) {
+    console.log("team_members_admin_rules: team_members does not exist — skipping.");
+    return;
+  }
+  if (col.type !== "auth") {
+    console.log("team_members_admin_rules: team_members is not an auth collection — skipping.");
+    return;
+  }
+  col.updateRule = UPDATE_RULE;
+  col.deleteRule = DELETE_RULE;
+  app.save(col);
+}, (app) => {
+  // Down: restore the previous (self-update only, superuser delete) rules.
+  let col;
+  try {
+    col = app.findCollectionByNameOrId("team_members");
+  } catch (_) {
+    return;
+  }
+  if (col.type !== "auth") {
+    return;
+  }
+  col.updateRule = '@request.auth.id = id';
+  col.deleteRule = null;
+  app.save(col);
+});