Require document helper in Linux headless packages and verify Unix worker

docs/BUILDING.md

@@ -304,3 +304,10 @@ it with `python tools/stage_extraction_worker.py` before desktop development or
 release packaging. Release builds reject a missing helper. Headless deployments
 place the platform helper beside the CLI executable. Parser failure retains
 filename search and exposes an extraction error; there is no in-process fallback.
+
+For Linux headless archive preparation, stage the extraction helper into the
+same directory passed to `package_linux.py --runtime`:
+
+```sh
+python tools/stage_extraction_worker.py --destination .searchi/runtime/auto
+```

docs/EXTRACTION-ISOLATION.md

@@ -178,3 +178,18 @@ its actual entries. The helper extracted from that archive passed genuine PDF
 indexing through the normal adapter (1.76 s). Archive SHA-256:
 `760259bbf07ed076857f0e47c0b536eb352e4d00973701bfe115d95f41989daf`.
 This archive is local evidence; a new installer has not been published.
+
+## Linux headless consistency
+
+The Linux packager now requires a current verified helper/inventory in its
+runtime directory, checks x86-64 ELF/system dependency closure and executable
+archive mode. Nineteen package tests passed normally and with Python `-O`.
+Missing/stale/tampered helpers and unsupported dependencies preserve output.
+
+An immutable source snapshot at `18ce700` executed four actual worker/parent
+integration tests under Ubuntu WSL, CPU only: real DOCX, corrupt PDF, exact
+source digest, cancellation distinction and malformed protocol rejection.
+Unix resource setup executed; adversarial exhaustion was not tested. The initial
+WSL nested-virtualization warning did not prevent the terminal passing Cargo run.
+The public Linux archive remains the earlier release; updated archive build and
+relocated index checks remain open.