feat(ansible): runs stay inside their source; controller-side vars are admin-only (#5034)

#5034 "Playbook runs: path and inventory checks in trigger_run, connection
vars admin-only, confirm enforced server-side, web actions audited".
Ansible runs inside the Steward container, so an operator who could name
any playbook path, set ansible_connection=local or ProxyCommand ssh args,
or put {{ lookup('pipe', …) }} in a value could run commands on Steward.

- steward/ansible/guards.py: check_playbook (the source must list it),
  check_inventory_scope (steward:* or an inventory file the source has),
  check_vars_for_role (ansible_* beyond host/port/user/password/become,
  and any Jinja in a value, are admin-only), changed_vars (an edit is
  held to the role only for what it changes).
- trigger_run applies the path checks, so every run path — web, MCP,
  alerts, schedules, plugins — gets them.
- Variables are checked by role on the web run form, host-page runs,
  schedule create/update, inventory group/target create/update, and MCP
  run_playbook / create_schedule / update_schedule.
- A steward:confirm playbook needs the confirmation ticked on the server
  side for a real (non-check) web run, as MCP already required.
- Audited: runs, cancel, schedule create/update/enable/disable/delete/
  run-now, playbook create/update/delete, inventory group and target
  create/update/delete (variable names only, never values). One
  audit_request helper serves the web routes.
- The CSRF form guard and the route guard now each test that they fail
  on a synthetic broken input (rule: a guard must be able to fail).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/core/audit.py

@@ -38,3 +38,11 @@ async def log_audit(
                 ))
     except Exception:
         logger.exception("Failed to write audit event action=%r", action)
+
+
+async def audit_request(action: str, entity_type: str | None = None,
+                        entity_id: str | None = None, detail: dict | None = None) -> None:
+    """log_audit for the logged-in user of the current web request."""
+    from quart import current_app, session
+    await log_audit(current_app, session.get("user_id"), session.get("username", ""),
+                    action, entity_type=entity_type, entity_id=entity_id, detail=detail)