Add readable operand decode and register def-use analysis

insndec.h: insn_decode() decodes one instruction into a readable form -
concrete registers as canonical roots (al/ah/ax/eax/rax -> one root), memory
base/index/scale/disp, immediate values, operand sizes, per-operand read/write,
and implicit operands/effects (rsp on push/pop, rdx:rax on mul/div, FLAGS). It
is ABI-agnostic: a call reports only its architectural effects.

codetrace.h: func_usedef(fn, abi, ...) computes per-instruction register
use/def over a function view (reusing cfg_blocks), splitting writes into
full-kill / partial / conditional so a reaching-definitions pass can be built on
top. With TRACE_ABI_WIN64 it marks the Win64 caller-saved set
(rax,rcx,rdx,r8-r11,xmm0-5,flags) clobbered at each call site; the clobber table
is confined to codetrace.c and the generic layer stays OS-agnostic
(TRACE_ABI_NONE keeps the conservative behaviour).

Both ride the existing optional disassembler seam (a second insn_decode_full
is added to semsig_backend.h; sem_insn and semsig_hash are untouched), gated
behind VMIE_HAVE_DISASM; OFF builds a stub. Adds the vmie_win32_func_usedef
wrapper. No new build option - the feature shares VMIE_DISASM with semsig.

CMakeLists.txt

@@ -49,12 +49,17 @@ add_library(vmie_obj OBJECT
 # backend TU that talks to the disassembler. semsig.c is never built in OFF (it
 # calls the backend decode, absent there) - so there is no dead/unresolved call.
 if(VMIE_DISASM STREQUAL "OFF")
-    target_sources(vmie_obj PRIVATE src/handlers/semsig_stub.c)
+    target_sources(vmie_obj PRIVATE src/handlers/semsig_stub.c
+                                    src/handlers/insndec_stub.c)
 elseif(VMIE_DISASM STREQUAL "zydis")
     target_sources(vmie_obj PRIVATE src/handlers/semsig.c
+                                    src/handlers/insndec.c
+                                    src/handlers/codetrace.c
                                     src/handlers/semsig_backend_zydis.c)
 elseif(VMIE_DISASM STREQUAL "capstone")
     target_sources(vmie_obj PRIVATE src/handlers/semsig.c
+                                    src/handlers/insndec.c
+                                    src/handlers/codetrace.c
                                     src/handlers/semsig_backend_capstone.c)
 else()
     message(FATAL_ERROR "VMIE_DISASM must be OFF, zydis, or capstone (got '${VMIE_DISASM}')")