fix(iso): make memtest non-blocking by default

bible-local/decisions/2026-04-01-memtest-build-strategy.md

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+# Decision: Treat memtest as explicit ISO content, not as trusted live-build magic
+
+**Date:** 2026-04-01
+**Status:** active
+
+## Context
+
+We have already iterated on `memtest` multiple times and kept cycling between the same ideas.
+The commit history shows several distinct attempts:
+
+- `f91bce8` — fixed Bookworm memtest file names to `memtest86+x64.bin` / `memtest86+x64.efi`
+- `5857805` — added a binary hook to copy memtest files from the build tree into the ISO root
+- `f96b149` — added fallback extraction from the cached `.deb` when `chroot/boot/` stayed empty
+- `d43a9ae` — removed the custom hook and switched back to live-build built-in memtest integration
+- `60cb8f8` — restored explicit memtest menu entries and added ISO validation
+- `3dbc218` / `3869788` — added archived build logs and better memtest diagnostics
+
+Current evidence from the archived `easy-bee-nvidia-v3.14-amd64` logs dated 2026-04-01:
+
+- `lb binary_memtest` does run and installs `memtest86+`
+- but the final ISO still does **not** contain `boot/memtest86+x64.bin`
+- the final ISO also does **not** contain memtest menu entries in `boot/grub/grub.cfg` or `isolinux/live.cfg`
+
+So the assumption "live-build built-in memtest integration is enough on this stack" is currently false for this project until proven otherwise by a real built ISO.
+
+## Decision
+
+For `bee`, memtest must be treated as an explicit ISO artifact with explicit post-build validation.
+
+Project rules from now on:
+
+- Do **not** trust `--memtest memtest86+` by itself.
+- A memtest implementation is considered valid only if the produced ISO actually contains:
+  - `boot/memtest86+x64.bin`
+  - `boot/memtest86+x64.efi`
+  - a GRUB menu entry
+  - an isolinux menu entry
+- If live-build built-in integration does not produce those artifacts, use an explicit project-owned mechanism such as:
+  - a binary hook copying files into `binary/boot/`
+  - extraction from the cached `memtest86+` `.deb`
+  - another deterministic build-time copy step
+- Do **not** remove such explicit logic later unless a fresh real ISO build proves that built-in integration alone produces all required files and menu entries.
+
+Current implementation direction:
+
+- keep the live-build memtest stage enabled if it helps package acquisition
+- but enforce memtest explicitly in a project-owned binary hook
+- patch the generated `binary/boot/grub/grub.cfg` and `binary/isolinux/live.cfg` directly in the binary stage if memtest entries are missing
+
+## Consequences
+
+- Future memtest changes must begin by reading this ADR and the commits listed above.
+- We should stop re-introducing "prefer built-in live-build memtest" as a default assumption without new evidence.
+- Memtest validation in `build.sh` is not optional; it is the acceptance gate that prevents another silent regression.
+- If we change memtest strategy again, we must update this ADR with the exact build evidence that justified the change.