Add virtual memory support: PE_MMU, VA allocator, fabric MmuMapMsg

Implement VA/MMU layer (ADR-0011 Phase 1) enabling Triton kernels to use
contiguous virtual addresses on sharded tensors.

Key changes:
- PE_MMU component: hybrid inbox (MmuMapMsg) + sync translate() for PE_DMA
- VirtualAllocator + PEMemAllocator: free-list with coalescing
- MmuMapMsg/MmuUnmapMsg fabric path with SIP-level routing
- DPPolicy-based mapping: replicate=local, sharded=broadcast
- Tensor lifecycle: del + weakref cleanup, context manager
- Rename: TensorHandle.pa→addr, DmaReadCmd.src_pa→src_addr, ctx→torch

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

tests/test_topology_load.py

@@ -23,7 +23,7 @@ def test_pe_template_components():
     spec = _read_spec(TOPOLOGY_PATH)
     comps = spec["cube"]["pe_template"]["components"]
     assert set(comps.keys()) == {
-        "pe_cpu", "pe_scheduler", "pe_dma", "pe_gemm", "pe_math", "pe_tcm"
+        "pe_cpu", "pe_scheduler", "pe_dma", "pe_gemm", "pe_math", "pe_mmu", "pe_tcm"
     }