Wire PE_MMU to router mesh for MmuMapMsg delivery

Add router → PE_MMU edge so MmuMapMsg can reach PE_MMU via
the router mesh. Unskip all PE_MMU fabric tests.

339 passed, 0 skipped

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_mmu_fabric.py

@@ -13,8 +13,6 @@ Validates:
 import pytest
 from pathlib import Path
 
-pytestmark = pytest.mark.skip(reason="PE_MMU routing via router mesh not yet wired (ADR-0019)")
-
 from kernbench.policy.address.allocator import AddressConfig, PEMemAllocator
 from kernbench.policy.address.pe_mmu import PeMMU
 from kernbench.policy.address.va_allocator import VirtualAllocator