feat(binary-layout): admit ELF32 i386, ARM and MIPS layout profiles (#7052)

* feat(binary-layout): admit ELF32 i386, ARM and MIPS layout profiles

inspect_binary_layout refused every ELF32 object, so router and IoT
firmware (ARM32, MIPS32) got no layout facts at all.

The pwntools adapter now admits EXEC/DYN/REL objects in these profiles:
ELF64 x86-64, ELF32 i386, ELF32 little-endian ARM and ELF32 little- or
big-endian MIPS. Header fields are read in the declared byte order, the
ELF32 header is bounds-checked at 52 bytes, and pwntools' own reported
architecture, class and byte order must match the admitted profile.
Other machines, classes and byte orders keep an unsupported_target
refusal that names the admitted profiles.

The output schema admits exactly those architecture combinations, and
the Evidence subject now names the reported machine instead of always
claiming x86_64.

verify:binary:layout cross-compiles i386, ARM, MIPS and MIPSel
executables and relocatable objects (never executed) and checks every
section name, address, offset and size against GNU readelf through CLI
and MCP. The real-binary-layout workflow installs those toolchains.

Refs #6934

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* ci(binary-layout): install target libc headers for ELF32 fixtures

--no-install-recommends skips the libc6-dev-*-cross packages the cross
compilers only recommend, so the i686 fixture fell back to the host's
/usr/include and failed to find bits/libc-header-start.h. Install the
four target libc development packages explicitly.

Refs #6934

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* fix(binary-layout): size the minimum symbol entry by ELF class

The relocation reference check required a 24-byte Elf64_Sym entry, so
every positive symbol reference in an ELF32 report was refused as
unreadable output. Elf32_Sym is 16 bytes; take the minimum from the
reported class. A 64-bit table with 16-byte entries is still refused.

Refs #6934

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test(binary-layout): compare ELF32 symbols and relocations with readelf

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: morluto <76467478+morluto@users.noreply.github.com>

.github/workflows/real-binary-layout.yml

@@ -55,6 +55,12 @@ jobs:
       - uses: ./.github/actions/portable-build-cache
         with:
           build_cache_artifact: ${{ inputs.build_cache_artifact }}
+      - name: Install ELF32 cross toolchains for source-owned fixtures
+        run: |
+          sudo apt-get update
+          sudo apt-get install --yes --no-install-recommends \
+            gcc-i686-linux-gnu gcc-arm-linux-gnueabi gcc-mips-linux-gnu gcc-mipsel-linux-gnu \
+            libc6-dev-i386-cross libc6-dev-armel-cross libc6-dev-mips-cross libc6-dev-mipsel-cross
       - name: Acquire exact upstream libraries in an isolated runner environment
         shell: bash
         run: |