feat(emu,frida): capture Windows TEB and seed x86 segment base

[ricardojrdez]

What

Frida's CpuContext exposes no segment base, so every Frida-acquired slice had
fs/gs base = 0 and peb = None, and the Unicorn emulator could not run x86 SEH
prologues that read the TEB via fs:[0].

• Capture (frida_bridge): on Windows, resolve each thread's TEB via
  OpenThread + NtQueryInformationThread(ThreadBasicInformation) and record it as
  gs_base (x64) / fs_base (ia32). Version-robust export resolution across Frida
  API generations.
• Emulator (emu/engine): in 32-bit mode Unicorn ignores
  UC_X86_REG_FS_BASE/GS_BASE, so install a synthetic GDT (flat ring-3 data
  descriptor) for each captured base and load the matching selector;
  segment_base()/peb_address() now work on x86. x64 already honored gs_base
  directly.

Verification

• Confirmed empirically that Frida's CpuContext exposes no segment base (attaching
  to a live x64 process: fs/gs/fs_base/gs_base all undefined).
• Unicorn 2.1.4: x64 honors gs_base; on x86 the fs_base write is a no-op → the GDT
  trick fixes it.
• New tests: x86 GDT path (fs:[0x30]→PEB), no-base case (no regression), and
  segment-base flow through the Frida bridge.
• Full suite: 1142 passed / 10 skipped, ruff clean. JS validated by loading it in
  the real Frida engine.

🤖 Generated with Claude Code