Rename impl names: add builtin. prefix for clear provenance

- components.yaml: all builtin impls use builtin.xxx naming
- topology.yaml: all impl references updated to builtin.xxx
- builder.py: hardcoded ucie impl → builtin.ucie
- Tests: all impl string references updated

Convention: builtin.<name> for built-in, custom.<name> for user-defined.
382 tests passing.

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

tests/test_mmu_component.py

@@ -71,7 +71,7 @@ def test_mmu_unmap_msg_fields():
 
 
 def test_pe_mmu_registry():
-    """pe_mmu_v1 impl resolves in ComponentRegistry."""
+    """pe_mmu impl resolves in ComponentRegistry."""
     from kernbench.components.base import ComponentRegistry
     from kernbench.components.builtin.pe_mmu import PeMmuComponent
     from kernbench.topology.types import Node
@@ -79,7 +79,7 @@ def test_pe_mmu_registry():
     node = Node(
         id="sip0.cube0.pe0.pe_mmu",
         kind="pe_mmu",
-        impl="pe_mmu_v1",
+        impl="builtin.pe_mmu",
         pos_mm=None,
         attrs={"tlb_overhead_ns": 0.5},
     )
@@ -101,7 +101,7 @@ def test_pe_mmu_processes_map_msg():
     node = Node(
         id="sip0.cube0.pe0.pe_mmu",
         kind="pe_mmu",
-        impl="pe_mmu_v1",
+        impl="builtin.pe_mmu",
         pos_mm=None,
         attrs={"tlb_overhead_ns": 0.5, "page_size": 4096},
     )
@@ -158,7 +158,7 @@ def test_pe_dma_translates_va():
     node = Node(
         id="sip0.cube0.pe0.pe_dma",
         kind="pe_dma",
-        impl="pe_dma_v1",
+        impl="builtin.pe_dma",
         pos_mm=None,
         attrs={"rd_engines": 1, "wr_engines": 1},
     )