feat(permissions): admin no longer acts on the test workflow; managers coordinate operators

Admin administers the site — it no longer has any override on
validate-red/blue, review-red/blue, resolve-dispute, request-discussion,
reopen, hold, resume, assign-operators, or classification-update.
Introduces require_any_role_strict(), a role dependency without the
global admin bypass, so these specific endpoints truly exclude admin
instead of only removing it from the (redundant) role tuple.

Managers gain the ability to assign red_tech/blue_tech operators
(POST /tests/{id}/assign, GET /users/operators) alongside leads, since
that's coordination, not resolving a ticket.

Also enlarges and repositions the operator-assignment controls next
to the Start Execution button, and fixes a literal '\u2014' rendering
as text instead of an em dash in the test detail technique line.

backend/tests/test_assign_operators.py

@@ -1,4 +1,4 @@
-"""Tests for POST /tests/{id}/assign — lead/admin manual operator assignment."""
+"""Tests for POST /tests/{id}/assign — lead/manager manual operator assignment."""
 
 from unittest.mock import MagicMock, patch
 
@@ -67,6 +67,32 @@ def test_red_tech_cannot_assign(client, db, red_tech_headers, red_tech_user):
     assert resp.status_code == 403
 
 
+def test_admin_cannot_assign(client, db, auth_headers, admin_user, red_tech_user):
+    """Admin administers the site — coordinating operators is a lead/manager call."""
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, admin_user.id)
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"red_tech_assignee": str(red_tech_user.id)},
+        headers=auth_headers,
+    )
+    assert resp.status_code == 403
+
+
+def test_manager_can_assign(client, db, manager_headers, manager_user, red_tech_user):
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, manager_user.id)
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"red_tech_assignee": str(red_tech_user.id)},
+        headers=manager_headers,
+    )
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["red_tech_assignee"] == str(red_tech_user.id)
+
+
 def test_clearing_assignee_does_not_touch_jira(client, db, red_lead_headers, red_lead_user, red_tech_user):
     """Sending null explicitly clears the assignee without a Jira sync call."""
     technique = _seed_technique(db)