Package portable Linux runtime and verify Google CPU search

docs/BUILDING.md

@@ -97,6 +97,11 @@ These are the current script and CLI interfaces, not evidence of an executed
 Linux release. On a native Linux build host with Vulkan development libraries
 and `glslc`, run from the repository root:
 
+On Ubuntu 24.04, the native worker build prerequisites are `build-essential`,
+`cmake`, `git`, `pkg-config`, `libvulkan-dev`, `glslc`, and `spirv-headers`.
+The last package supplies the SPIR-V CMake configuration required by the pinned
+Vulkan backend. These build tools do not enable GPU execution in tests.
+
 ```sh
 python3 tools/embeddinggemma2/build_runtime.py --backend auto --jobs 2
 python3 tools/embeddinggemma2/download.py
@@ -114,6 +119,46 @@ This normal worker detects usable acceleration and falls back to CPU. Internal
 CPU-only model tests may use `--backend cpu` and `SEARCHI_FORCE_CPU=1`; those
 test artifacts are not a separate distribution edition.
 
+### Linux headless archive validation
+
+The Linux x86-64 normal worker layout includes baseline and optimized CPU
+modules, an optional Vulkan module and adjacent core libraries. The builder
+audits ELF dependencies and origin-relative lookup before writing a hashed
+runtime inventory. ARM and other distribution/ABI combinations remain separate
+release gates.
+
+After building the normal worker, release CLI and pinned media helpers, prepare
+an unsigned headless development candidate:
+
+```sh
+python3 tools/package_linux.py
+python3 tools/embeddinggemma2/linux_smoke.py --worker .searchi/runtime/auto/searchi-gemma-worker --models .searchi/models/embeddinggemma2 --output .searchi/packages/linux-worker-smoke.json
+python3 tools/embeddinggemma2/linux_smoke.py --worker .searchi/runtime/auto/searchi-gemma-worker --models .searchi/models/embeddinggemma2 --output .searchi/packages/linux-baseline-smoke.json --baseline
+```
+
+The packager accepts explicit `--executable`, `--runtime`, `--media` and
+`--llama-license` paths when builds use separate target/cache directories.
+It packages only approved runtime files, pinned decoders and notices, with
+normalized archive metadata, executable modes and per-file checksums. It
+excludes model caches and user indexes/settings. The smoke checks copy the
+runtime outside its build tree and run genuine Google code inference on CPU;
+the baseline check omits optimized CPU modules from its temporary extraction.
+They do not exercise GPU providers or certify older physical CPUs, installers
+or desktop behavior. Archive extraction and installed CLI search must also
+be verified before a release gate is closed.
+
+The optional Linux missing-loader check requires explicit root execution and
+util-linux mount namespaces/chroot. It never escalates privileges and verifies
+a private namespace before creating an isolated filesystem:
+
+```sh
+sudo python3 tools/embeddinggemma2/linux_loader_smoke.py --worker .searchi/runtime/auto/searchi-gemma-worker --models .searchi/models/embeddinggemma2 --output .searchi/packages/linux-missing-loader.json
+```
+
+It runs automatic device selection with no forced-CPU override, but contains no
+Vulkan loader, driver configuration or GPU devices, so only CPU inference can
+execute. This is distinct from testing an actual GPU or recovering device loss.
+
 `searchi setup --model-dir PATH` is an alternative verified model-provisioning
 command. It provisions model assets, not the native worker. Package the worker
 separately and pass its path to headless embedding/search. Each short-lived CLI