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>

v3/src/word_source/README.md

@@ -0,0 +1,51 @@
+# src/word_source/
+
+FORTH-79 word implementations, one file per category, registered into the
+dictionary via `include/word_registry.h`. Each `.c` file here has a
+matching header in `src/word_source/include/` and (for most categories) a
+matching test module in `src/test_runner/modules/`.
+
+**FORTH-79 core**
+- `arithmetic_words.c`, `mixed_arithmetic_words.c` — `+ - * / MOD ABS MIN
+  MAX` and mixed-precision arithmetic.
+- `stack_words.c` — `DUP DROP SWAP ROT OVER NIP TUCK`.
+- `control_words.c` — `IF ELSE THEN DO LOOP BEGIN UNTIL WHILE`.
+- `defining_words.c` — `: ; CREATE DOES> VARIABLE CONSTANT`.
+- `memory_words.c` — `@ ! C@ C! MOVE FILL`.
+- `return_stack_words.c` — `>R R> R@ RDROP 2>R 2R@ 2R>`.
+- `double_words.c` — `2DUP 2DROP 2SWAP 2@ 2! D+ D-`.
+- `logical_words.c` — `AND OR XOR NOT INVERT LSHIFT RSHIFT`.
+- `io_words.c` — `EMIT KEY TYPE CR TAB SPACE ACCEPT`.
+- `string_words.c` — `S" SLITERAL` and other string operations.
+- `block_words.c` — `BLOCK BUFFER LOAD THRU FLUSH`.
+- `format_words.c` — `.( .R .S HEX DECIMAL BASE`.
+- `system_words.c` — `BYE ABORT INCLUDE STATE`.
+- `dictionary_words.c` — `FIND SEARCH-WORDLIST WORDS`.
+- `dictionary_manipulation_words.c` — dictionary entry manipulation words.
+- `vocabulary_words.c` — `VOCABULARY DEFINITIONS FORTH-WORDLIST`.
+- `editor_words.c` — block editor words.
+- `defer_words.c` — `DEFER`/`IS` deferred-word mechanism, used by the
+  Tripod message-dispatch shim (see `tools/hermes_tripod_smoke.sh`).
+
+**StarForth-specific extensions**
+- `q48_16_words.c`, `q48_words.c` — Q48.16 fixed-point word bindings.
+- `starforth_words.c` — StarForth-specific extensions.
+- `acl_words.c` — word-level ACL system's FORTH-callable primitives (see
+  `docs/03-architecture/word-acl/`).
+- `lifecycle_words_hosted.c` — hosted-build VM lifecycle words (birth/run
+  primitives on the hosted side; kernel-only primitives live in
+  `src/starkernel/capsule/mama_forth_words.c`).
+- `log_words.c` — FORTH-callable logging primitives.
+- `inference_words.c` — FORTH-callable bindings for the statistical
+  inference engine (Loops #5/#6).
+- `physics_benchmark_words.c` — benchmark harness for the 7 physics
+  feedback loops.
+- `physics_diagnostic_words.c` — physics diagnostics (`WORD-ENTROPY`).
+- `physics_freeze_words.c` — `PHYSICS-FREEZE` / `PHYSICS-THAW`.
+- `physics_pipelining_diagnostic_words.c` — Loop #4 pipelining
+  diagnostics.
+- `dictionary_heat_diagnostic_words.c` — Loop #1 heat diagnostics.
+
+See `src/word_source/include/` for the matching headers (also includes
+`mama_forth_words.h`, whose `.c` implementation lives under
+`src/starkernel/capsule/` since it's kernel-only).