app/agents/shared/middleware/permission.py was an older, monolithic
PermissionMiddleware superseded by the modular permissions/ package under
multi_agent_chat/shared/middleware/ (core + evaluation + ask/ + factory).
Production wires only the package (main_agent stack + every subagent
builder); the kernel file was reachable only through the shared barrel
re-export (itself unused) and two tests pinned to its dead internals
(_raise_interrupt, _normalize_permission_decision, old after_model shape).
- delete app/agents/shared/middleware/permission.py
- drop PermissionMiddleware from the shared middleware barrel
- delete test_permission_middleware.py (covered the dead impl only; live
behavior is covered by tests/.../middleware/shared/permissions/*)
- test_desktop_safety_rules.py: keep the ruleset-level regression tests,
drop the dead import + TestPermissionMiddlewareIntegration class