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/capsule_generated.h

@@ -0,0 +1,63 @@
+/*
+  StarForth — Steady-State Virtual Machine Runtime
+  Copyright (c) 2023–2025 Robert A. James
+  All rights reserved.
+  Licensed under the StarForth License, Version 1.0
+*/
+
+/**
+ * capsule_generated.h - Declarations for mkcapsule-generated capsule store.
+ *
+ * The matching capsule_generated.c is produced at build time by mkcapsule.
+ * These three arrays plus the directory header are compiled into .rodata.
+ */
+
+#ifndef STARKERNEL_CAPSULE_GENERATED_H
+#define STARKERNEL_CAPSULE_GENERATED_H
+
+#include <stdint.h>
+#include "starkernel/capsule.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Mark as hidden so GCC uses direct RIP-relative addressing in PIC/PE builds,
+ * avoiding GOT references which do not exist in PE/COFF binaries. */
+__attribute__((visibility("hidden")))
+extern const uint8_t         capsule_arena[];
+__attribute__((visibility("hidden")))
+extern const CapsuleDesc     capsule_descriptors[];
+__attribute__((visibility("hidden")))
+extern const CapsuleNameEntry capsule_names[];
+__attribute__((visibility("hidden")))
+extern const CapsuleSigEntry capsule_signatures[];
+__attribute__((visibility("hidden")))
+extern const CapsuleDirHeader capsule_directory;
+
+/*
+ * Accessor functions — defined in the same TU as the symbols above.
+ * PE/COFF builds with -fPIC do not convert GOTPCREL data references to
+ * direct LEA the way the ELF linker does, so any cross-TU access to a
+ * data symbol goes through GOT and reads garbage in a PE image.
+ * These hidden accessor functions are called via a direct CALL (no PLT/GOT)
+ * and access the symbols with direct RIP-relative addressing inside their TU.
+ */
+__attribute__((visibility("hidden")))
+uint32_t                   capsule_get_desc_count(void);
+__attribute__((visibility("hidden")))
+const CapsuleDirHeader    *capsule_get_directory(void);
+__attribute__((visibility("hidden")))
+const CapsuleDesc         *capsule_get_descriptors(void);
+__attribute__((visibility("hidden")))
+const CapsuleNameEntry    *capsule_get_names(void);
+__attribute__((visibility("hidden")))
+const CapsuleSigEntry     *capsule_get_signatures(void);
+__attribute__((visibility("hidden")))
+const uint8_t             *capsule_get_arena(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* STARKERNEL_CAPSULE_GENERATED_H */