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/capsule/vm_uuid.c

@@ -0,0 +1,137 @@
+/*
+  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.
+
+ */
+
+/**
+ * vm_uuid.c - 128-bit VM identifiers (FABRIC-0.md punch list item 3.8)
+ *
+ * See vm_uuid.h for the design rationale (no RNG source exists on any of
+ * the three ISAs uniformly, so this is deterministic, not random).
+ */
+
+#include "starkernel/vm_uuid.h"
+
+#ifdef __STARKERNEL__
+
+#include <stddef.h>
+
+#define VM_UUID_POOL_SIZE 16
+
+static uint64_t vm_uuid_prng_state  = 0;
+static int      vm_uuid_seeded      = 0;
+static VMUuid   vm_uuid_pool[VM_UUID_POOL_SIZE];
+static size_t   vm_uuid_pool_pos    = VM_UUID_POOL_SIZE; /* "empty": first next() call refills */
+
+VMUuid vm_uuid_hera(void) {
+    VMUuid id;
+    id.hi = 0;
+    id.lo = 0;
+    return id;
+}
+
+int vm_uuid_is_hera(VMUuid id) {
+    return id.hi == 0 && id.lo == 0;
+}
+
+VMUuid vm_uuid_none(void) {
+    VMUuid id;
+    id.hi = 0xFFFFFFFFFFFFFFFFULL;
+    id.lo = 0xFFFFFFFFFFFFFFFFULL;
+    return id;
+}
+
+int vm_uuid_is_none(VMUuid id) {
+    return id.hi == 0xFFFFFFFFFFFFFFFFULL && id.lo == 0xFFFFFFFFFFFFFFFFULL;
+}
+
+int vm_uuid_equal(VMUuid a, VMUuid b) {
+    return a.hi == b.hi && a.lo == b.lo;
+}
+
+/* splitmix64 -- public-domain, well-known, minimal. Deterministic given a
+ * seed; not cryptographically random, not claimed to be. */
+static uint64_t splitmix64_next(uint64_t *state) {
+    uint64_t z = (*state += 0x9E3779B97F4A7C15ULL);
+    z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ULL;
+    z = (z ^ (z >> 27)) * 0x94D049BB133111EBULL;
+    return z ^ (z >> 31);
+}
+
+static void vm_uuid_pool_refill(void) {
+    size_t i;
+    for (i = 0; i < VM_UUID_POOL_SIZE; i++) {
+        uint64_t hi = splitmix64_next(&vm_uuid_prng_state);
+        uint64_t lo = splitmix64_next(&vm_uuid_prng_state);
+        /* RFC 4122 version 4 / variant bits -- cosmetic shape only, not a
+         * claim these are cryptographically random. */
+        hi = (hi & 0xFFFFFFFFFFFF0FFFULL) | 0x0000000000004000ULL;
+        lo = (lo & 0x3FFFFFFFFFFFFFFFULL) | 0x8000000000000000ULL;
+        vm_uuid_pool[i].hi = hi;
+        vm_uuid_pool[i].lo = lo;
+    }
+    vm_uuid_pool_pos = 0;
+}
+
+void vm_uuid_pool_init(uint64_t seed) {
+    vm_uuid_prng_state = seed;
+    vm_uuid_seeded = 1;
+    vm_uuid_pool_refill();
+}
+
+VMUuid vm_uuid_next(void) {
+    VMUuid id;
+
+    if (!vm_uuid_seeded) {
+        /* Safety net, not the intended path -- callers should seed from the
+         * Mama capsule's content hash before the first non-Hera VM birth. */
+        vm_uuid_pool_init(0x9E3779B97F4A7C15ULL);
+    }
+    if (vm_uuid_pool_pos >= VM_UUID_POOL_SIZE) {
+        vm_uuid_pool_refill();
+    }
+
+    id = vm_uuid_pool[vm_uuid_pool_pos];
+    vm_uuid_pool_pos++;
+    return id;
+}
+
+void vm_uuid_format(VMUuid id, char *buf) {
+    static const char hex[] = "0123456789abcdef";
+    int pos = 0;
+    int i;
+    uint64_t halves[2];
+    /* Group boundaries per RFC 4122: 8-4-4-4-12 hex digits, dashes after
+     * digit 8, 12, 16, 20 (of 32 total). hi supplies digits 0-15, lo
+     * supplies digits 16-31. */
+    halves[0] = id.hi;
+    halves[1] = id.lo;
+
+    for (i = 0; i < 32; i++) {
+        uint64_t v = (i < 16) ? halves[0] : halves[1];
+        int shift = (15 - (i % 16)) * 4;
+        buf[pos++] = hex[(v >> shift) & 0xF];
+        if (i == 7 || i == 11 || i == 15 || i == 19) buf[pos++] = '-';
+    }
+    buf[pos] = '\0';
+}
+
+#endif /* __STARKERNEL__ */