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/README.md

@@ -0,0 +1,12 @@
+# bee — Project Bible
+
+Project-specific architecture, decisions, and runtime contracts.
+Generic engineering rules live in `bible/rules/patterns/`.
+
+## Files
+
+| File | Contents |
+|---|---|
+| `architecture/system-overview.md` | What bee does, scope, tech stack |
+| `architecture/runtime-flows.md` | Boot sequence, audit flow, service order |
+| `decisions/` | Architectural decision log |