feat: DGR-005-003-CHAIN - DGR-005 + DGR-003-emission + anchor

.scratch/distributed-gguf-runtime/evidence/DGR-005/DECOMPOSITION.md

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+# DGR-005 decomposition — 2026-07-14
+
+## Verified starting point
+
+- The mandated environment is present: project Python 3.14.6, CMake 4.4.0,
+  and protobuf 7.35.1.
+- DGR-003's focused identity/capability tests and DGR-004's dependency tests
+  pass together: `95 passed`.
+- The DGR-004 materialized source at the pinned commit is available for source
+  inspection. It contains only the DGR-004 CMake-marker patch.
+
+## Why this chain cannot safely claim DGR-005 yet
+
+At the locked llama.cpp revision, `llama_model_base::load_tensors()`:
+
+1. sizes `layers` to `hparams.n_layer_all`;
+2. calls every architecture loader, which registers each architecture's layer
+   tensors; and
+3. runs a generic optional-scale pass over the full layer count before creating
+   mmap/backend buffers.
+
+Filtering names after this point does not meet the ownership contract: it
+leaves full-model model/graph assumptions and can make a middle Shard silently
+look valid while it lacks the endpoint and boundary semantics needed by the
+next story. A generic `blk.N.*` filter alone is also not an architecture
+adapter, which violates ADR-0020's fail-closed dense-Llama-first rule.
+
+## Required child slices
+
+1. **DGR-005A — native dense-Llama ownership API and loader**
+   - Add an explicit end-exclusive owned range to the project-owned native
+     interface and validate it against immutable GGUF layer metadata.
+   - Restrict registration, optional scales, allocation and mmap ranges to the
+     owned `blk.N.*` tensors.
+   - Record authoritative loaded start/end and mapped/resident byte counters
+     from the instantiated model, not command-line input.
+   - Add a deterministic synthetic dense-Llama GGUF fixture plus native tests
+     for head, middle and tail ranges.
+
+2. **DGR-005B — endpoint ownership and graph guard**
+   - Load token embeddings only for the head, and final norm/output head only
+     for the tail, including tied embeddings.
+   - Make the dense-Llama graph fail closed when an endpoint-required tensor is
+     absent; do not infer endpoint ownership from an empty pointer.
+   - Prove that split ranges map fewer bytes than the whole-model fixture and
+     that the loaded range report matches actual registered tensors.
+
+3. **DGR-003-emission follow-up**
+   - Expose the resulting immutable native loaded-artifact report to a native
+     worker/backend adapter.
+   - Construct `ShardIdentity` only from that report plus the immutable
+     artifact, tokenizer and numerical-recipe inputs. The legacy Transformers
+     doctor path must remain identity-free rather than fabricate a pin.
+   - Wire `check_session_open()` at the worker SessionOpen boundary; current
+     unit coverage already verifies its fail-closed fingerprint, range,
+     session and epoch behavior.
+
+## Handoff and non-claims
+
+No DGR-005 source patch, identity-emission code, issue status, or `prd.json`
+pass state was changed. No model was loaded, downloaded, benchmarked, or
+certified. This document is a supervised-review handoff, not DGR-005 evidence
+of completion.