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/src/boot/reloc_stub.c

@@ -0,0 +1,98 @@
+/*
+  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.
+
+ */
+
+/**
+ * reloc_stub.c - Provide a minimal .reloc section for PE/COFF EFI loader
+ *
+ * Some firmware refuses to load images without a Base Relocation Directory.
+ * This stub supplies an empty relocation block to satisfy the loader.
+ */
+
+#include <stdint.h>
+
+/**
+ * @brief PE/COFF Base Relocation Block header.
+ *
+ * Mirrors the @c IMAGE_BASE_RELOCATION layout from the PE specification:
+ * - @c page_rva   — RVA of the 4 KB page that the following entries apply to.
+ * - @c block_size — total byte size of this block including the header and
+ *                   all entries (minimum 8 bytes for the header alone).
+ * - @c entry      — one or more 16-bit relocation entries packed as
+ *                   TYPE (4 bits) | OFFSET (12 bits); TYPE=0 / OFFSET=0
+ *                   is a no-op padding entry used to 32-bit-align the block.
+ *
+ * Marked @c packed to suppress any padding the compiler might insert between
+ * fields; @c aligned(4) ensures the block sits on a 4-byte boundary as
+ * required by the PE loader.
+ */
+struct reloc_block {
+    uint32_t page_rva;
+    uint32_t block_size;
+    uint16_t entry; /* TYPE=0, OFFSET=0 */
+} __attribute__((packed, aligned(4)));
+
+/**
+ * @brief Minimal @c .reloc section stub to satisfy UEFI firmware loaders.
+ *
+ * Some UEFI implementations (notably certain hardware vendor firmware and
+ * strict OVMF builds) refuse to load a PE32+ image that lacks a Base
+ * Relocation Directory entry in the optional-header Data Directory. Even
+ * for monolithic position-independent images that require no run-time fix-ups,
+ * the presence of the @c .reloc section with a well-formed (but empty)
+ * relocation block is required to pass the firmware's image validation.
+ *
+ * This single statically-allocated @c reloc_block satisfies the requirement:
+ * - @c page_rva = 0 — applies to the first 4 KB page (convention for stubs).
+ * - @c block_size = sizeof(reloc_block) — minimal well-formed block (8 bytes
+ *   + 2 bytes for the single no-op entry = 10 bytes).
+ * - @c entry = 0 — TYPE=0 (absolute, no-op) / OFFSET=0; ignored by the loader.
+ *
+ * The @c used attribute prevents the compiler/linker from discarding the
+ * symbol as unreferenced; the @c section(".reloc") attribute places it
+ * in the named PE section so the linker emits the correct Data Directory.
+ */
+__attribute__((section(".reloc"), used))
+static const struct reloc_block reloc_stub = {
+    .page_rva = 0,
+    .block_size = sizeof(struct reloc_block),
+    .entry = 0
+};