refactor(paged): stock llama-cpp is patch-free; paged backend owns its patch series

Move ALL paged-attention content out of the stock backend/cpp/llama-cpp
backend and into backend/cpp/llama-cpp-localai-paged, so the stock backend is
pure upstream llama.cpp and the paged backend owns and applies its own vendored
patch series.

- Delete the dead early-exploration scaffold backend/cpp/llama-cpp/paged/
  (kernel/w4a16 Marlin scaffold, standalone paged_kv_manager, bench/loadgen,
  its own 0001-0002 patches, dense-era design docs, tests). Zero references
  repo-wide.
- Move backend/cpp/llama-cpp/patches/ (the 28-patch paged series + paged/README
  + 3 operational docs, plus the kernel/ scaffold patch and the top-level paged
  README/BENCHMARKS) to backend/cpp/llama-cpp-localai-paged/patches/. The stock
  backend keeps no patches/ dir; it had no non-paged base patches.
- Purify the stock backend: remove the LLAMA_PAGED make variable, the
  patches/paged apply loop, and the LLAMA_PAGED passthrough to prepare.sh;
  remove the paged-series handling from prepare.sh. The stock llama.cpp target
  now only clones the pin and applies its own (currently empty) base patches/
  series. The runtime paged option hooks in the shared grpc-server.cpp are
  untouched (inert without the patches).
- The paged backend's Makefile now applies its OWN patches/paged/0*.patch onto
  each freshly cloned tree via strict git apply (apply-paged-patches), after the
  copied stock infra clones the pin and applies base patches.
- Repoint every reference to the old patches/paged path: the upstream canary
  workflow + apply script, bump_deps.yaml, gallery/index.yaml, the docs,
  backend/index.yaml, backend-matrix.yml, the top-level Makefile comments, and
  the moved PIN_SYNC / README docs. Drop the now-removed LLAMA_PAGED=on
  build-toggle from comments.

Verified: the full 28-patch series applies strict-clean (git apply, exit 0) to
a clean ggml-org/llama.cpp checkout at the pinned c299a92c, and the repointed
canary apply script resolves and applies the series end to end.

Assisted-by: Claude:opus-4.8 [Claude Code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

backend/cpp/llama-cpp/Makefile

@@ -6,14 +6,6 @@
 # bump and is advanced only by the manual PIN_SYNC process.
 LLAMA_VERSION?=9d5d882d8cd0f0a9283d87ed5e6fe3ee0d925fb1
 LLAMA_REPO?=https://github.com/ggerganov/llama.cpp
-# LLAMA_PAGED controls whether the vendored paged-attention patch series
-# (patches/paged/) is applied on top of the pinned llama.cpp. Default on; set
-# LLAMA_PAGED=off to build a clean-against-upstream backend (e.g. to unblock a
-# dep-bump if an upstream change breaks a paged hook - the paged carry is then
-# fixed independently). Runtime behaviour stays gated by the LLAMA_KV_PAGED env
-# regardless, so an LLAMA_PAGED=on build is byte-identical to stock until that
-# env is set.
-LLAMA_PAGED?=on
 
 CMAKE_ARGS?=
 BUILD_TYPE?=
@@ -187,23 +179,14 @@ llama.cpp:
 		[ -e "$$p" ] || continue; \
 		echo "applying llama.cpp patch: $$p"; \
 		git apply --verbose "$$p" || { echo "patch failed: $$p"; exit 1; }; \
-	done && \
-	if [ "$(LLAMA_PAGED)" = "off" ]; then \
-		echo "LLAMA_PAGED=off: skipping paged-attention patch series"; \
-	else \
-		for p in $(CURRENT_MAKEFILE_DIR)patches/paged/0*.patch; do \
-			[ -e "$$p" ] || continue; \
-			echo "applying llama.cpp PAGED patch: $$p"; \
-			git apply --verbose "$$p" || { echo "paged patch failed: $$p"; exit 1; }; \
-		done; \
-	fi
+	done
 
 llama.cpp/tools/grpc-server: llama.cpp
 	mkdir -p llama.cpp/tools/grpc-server
-	LLAMA_PAGED=$(LLAMA_PAGED) bash prepare.sh
+	bash prepare.sh
 
 rebuild:
-	LLAMA_PAGED=$(LLAMA_PAGED) bash prepare.sh
+	bash prepare.sh
 	rm -rf grpc-server
 	$(MAKE) grpc-server