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_tensor_free.py

@@ -76,7 +76,6 @@ def test_allocator_free_tcm_reclaims_space():
 # ── TF2. del tensor triggers cleanup ─────────────────────────────────
 
 
-@pytest.mark.skip(reason="PE_MMU routing via router mesh not yet wired")
 def test_del_tensor_unmaps_mmu():
     """del tensor removes MMU mappings."""
     ctx, engine = _make_ctx()