Reorganize source tree: kernel/, v3/, v4/ split and board infrastructure

Source tree reorganization:
- Move StarForth v3 engine to v3/ (src/, include/, Makefile)
- Move kernel to kernel/ (src/, include/, linker/, Makefile)
- Create v4/ skeleton for F18-ISA golden model (DECOMPOSITION.md, JUSTIFICATION.md)
- Move FABRIC-0..4.md to docs/fabric/
- Move ONTOLOGY.md and ROADMAP.md to docs/

Board infrastructure:
- Add boards/ser5/, boards/raspi/, boards/milkv/, boards/zynq7020/
- Each board has board.mk (ISA, CPU flags, boot recipe) and README.md
- Root Makefile becomes thin dispatcher: boot_image, all, clean, docs take TARGET
- make boot_image TARGET=SER5|RASPI|MILKV builds one GPT/MBR image per board
- ZYNQ7020 target exists but stops with clear error (ARMv7 port not built yet)
- scripts/mkdiskimage.sh builds disk images for all boards

Docs pipeline:
- docs/book/ with LaTeX master (main.tex) and Makefile
- pandoc converts Markdown to LaTeX at build time
- Two Lua filters: table-widths.lua (wide tables wrap), code-breaks.lua (inline code breaks)
- make docs builds single PDF (754 pages, 0 missing characters)
- make docs TARGET=<board> adds board appendix
- build/docs/<book|board>/meta.tex stamps git commit into PDF

Bug fixes:
- 42 include paths that only worked by accident now use correct relative paths
- clang-18 hardcode replaced with configurable CC variable (fixed aarch64 build)
- Pi 5: kernel_2712.img linked at 0x80000, .bss zeroed, memory reserved
- Doxyfile, .clang-tidy, README.md, Kconfig paths updated

Verified:
- Hosted v3 build passes 1012 tests, 0 failures
- SER5 image boots in QEMU (OVMF), POST passes, K exact (65536 = Q48_ONE)
- Milk-V image boots in QEMU (OpenSBI + U-Boot + bootefi), POST passes
- make clean TARGET=<board> removes only that board and its ISA objects
- make all builds all boards, hosted v3, and docs in one run

Co-authored-by: Junie <junie@jetbrains.com>

kernel/include/starkernel/vm/bootstrap/README.md

@@ -0,0 +1,6 @@
+# include/starkernel/vm/bootstrap/
+
+- `sk_vm_bootstrap.h` — declares the kernel VM bootstrap entry point
+  implemented in `src/starkernel/vm/bootstrap/sk_vm_bootstrap.c`. Owns
+  capsule loading and VM initialization wiring; deliberately kept separate
+  from `kernel_main.c`, which owns only hardware milestones.

kernel/include/starkernel/vm/bootstrap/sk_vm_bootstrap.h

@@ -0,0 +1,75 @@
+/*
+  StarForth — Steady-State Virtual Machine Runtime
+
+  Copyright (c) 2023–2025 Robert A. James
+  All rights reserved.
+
+  This file is part of the StarForth project.
+
+  Licensed under the StarForth License, Version 1.0 (the "License");
+  you may not use this file except in compliance with the License.
+
+  You may obtain a copy of the License at:
+      https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
+
+  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  express or implied, including but not limited to the warranties of
+  merchantability, fitness for a particular purpose, and noninfringement.
+
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+ StarForth — Steady-State Virtual Machine Runtime
+  Copyright (c) 2023–2025 Robert A. James
+  All rights reserved.
+
+  This file is part of the StarForth project.
+
+  Licensed under the StarForth License, Version 1.0 (the "License");
+  you may not use this file except in compliance with the License.
+
+  You may obtain a copy of the License at:
+       https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
+
+  This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  express or implied, including but not limited to the warranties of
+  merchantability, fitness for a particular purpose, and noninfringement.
+
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+ */
+
+/**
+ * sk_vm_bootstrap.h - Kernel VM bootstrap/parity entrypoints
+ *
+ * Gated by STARFORTH_ENABLE_VM so kernel images stay lean by default.
+ * Provides a single entry point that initializes the VM using kernel
+ * HAL services and emits the M7 parity packet.
+ */
+
+#ifndef STARKERNEL_VM_BOOTSTRAP_SK_VM_BOOTSTRAP_H
+#define STARKERNEL_VM_BOOTSTRAP_SK_VM_BOOTSTRAP_H
+
+#ifdef __STARKERNEL__
+
+#include "starkernel/vm/parity.h"
+
+/**
+ * sk_vm_bootstrap_parity - Initialize VM and emit parity packet.
+ *
+ * @param out Optional parity packet to fill (may be NULL to use a local)
+ * @return 0 on success, -1 on failure (see parity packet for details)
+ */
+int sk_vm_bootstrap_parity(ParityPacket *out);
+
+/**
+ * sk_get_mama_vm - Return opaque pointer to Mama's VM context.
+ *
+ * Valid after sk_vm_bootstrap_parity() succeeds.
+ */
+void *sk_get_mama_vm(void);
+
+#endif /* __STARKERNEL__ */
+
+#endif /* STARKERNEL_VM_BOOTSTRAP_SK_VM_BOOTSTRAP_H */