docs: add bible-local with architecture and decisions, fix PLAN.md versions

- bible-local/architecture/system-overview.md: scope, tech stack, key paths
- bible-local/architecture/runtime-flows.md: boot sequence, ISO build, collector flow
- bible-local/decisions/2026-03-05-nvidia-proprietary-driver.md
- PLAN.md: update KERNEL_VERSION 6.6→6.12, NVIDIA 550.54.15→590.48.01

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bible-local/decisions/2026-03-05-nvidia-proprietary-driver.md

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+# Decision: Use NVIDIA proprietary driver, not open kernel modules
+
+**Date:** 2026-03-05
+**Status:** active
+
+## Context
+
+bee needs to collect GPU serial numbers, VBIOS versions, and ECC telemetry via `nvidia-smi`.
+Two options exist: NVIDIA open-gpu-kernel-modules (MIT/GPLv2, GitHub) or the official
+proprietary `.run` installer.
+
+## Decision
+
+Use the official proprietary NVIDIA `.run` installer for both kernel modules and `nvidia-smi`.
+
+## Consequences
+
+- Kernel modules and nvidia-smi come from a single verified source.
+- NVIDIA publishes `.sha256sum` alongside each installer — download and verify before use.
+- Driver version pinned in `iso/builder/VERSIONS` as `NVIDIA_DRIVER_VERSION`.
+- Build process: download `.run`, extract, compile `kernel/` sources against `linux-lts-dev`.
+- Modules cached in `dist/nvidia-<version>-<kver>/` — rebuild only on version or kernel change.
+- ISO size increases by ~50MB for .ko files + nvidia-smi.

bible-local/decisions/README.md

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+# Architectural Decision Log
+
+One file per decision, named `YYYY-MM-DD-short-topic.md`.
+
+| Date | Decision | Status |
+|---|---|---|
+| 2026-03-05 | Use NVIDIA proprietary driver | active |