Fix Windows Cookbook background tasks, exit statuses, and empty SSH logs wrapper (#1389)

This commit consolidates all Windows Cookbook background fixes into a single comprehensive commit based on the latest main branch.

Key fixes included:
1. React looksSuccessful Mismatch: Append 'DOWNLOAD_OK' for pip install commands in routes/cookbook_routes.py.
2. Local Windows SSH Wrapper & Log Directory Mismatch: Bypassed ssh wrappers and dynamically selected odysseus-tmux logs for local tasks in static/js/cookbookRunning.js.
3. WSL Bash Filtration: Filtered out the WSL bash stub at C:\Windows\System32\bash.exe in core/platform_compat.py.
4. Drive-Colon Path Normalization: Replaced .as_posix() with git_bash_path() in routes/shell_routes.py and src/bg_jobs.py.
5. GGUF-Only Hardware Fitting: Restructured local Windows recommendations to rank GGUF only in services/hwfit/fit.py.
6. Safe Win32 Process Liveness Probe: Replaced os.kill(pid, 0) with a safe Win32 API probe using GetExitCodeProcess in core/platform_compat.py.
7. Prebuilt llama-cpp-python Wheels: Supply the CPU extra index during compilation failure fallback.
8. Enforce UTF-8 log encoding: Set PYTHONIOENCODING=utf-8 on Windows bootstrap runners.
9. Fix Linux Llama.cpp Build script syntax error in routes/cookbook_helpers.py.
10. Page Reload Status Check: Run sys.executable instead of 'python3' to bypass Microsoft Store execution stubs on local Windows hosts.
11. Llama.cpp serve build bypass: Bypassed cmake compilation checks on local Windows and verified python bindings directly.
12. Serve Command Path Validation: Masked safe GGUF path printf subshells '' inside the serve command validator.
13. CPU Mismatch Diagnostics: Intercepted AVX2-lacking '0xc000001d' (Illegal Instruction) crashes in static/js/cookbook-diagnosis.js and guided users to Ollama.
14. Windows Pytest stability: Fixed stub import leakage in test files.

routes/shell_routes.py

@@ -37,6 +37,7 @@ from core.platform_compat import (
     IS_WINDOWS,
     detached_popen_kwargs,
     find_bash,
+    git_bash_path,
 )
 
 
@@ -368,8 +369,12 @@ async def _create_shell(command: str, **kwargs):
     POSIX: /bin/sh via create_subprocess_shell (unchanged behaviour).
     Windows: prefer a real bash (Git Bash/WSL) so bash-syntax commands behave
     the same as on Linux; fall back to cmd.exe when no bash is installed.
+    Powershell commands are executed directly via cmd.exe /c to avoid quoting
+    and env variable expansion errors under Git Bash.
     """
     if IS_WINDOWS:
+        if command.strip().lower().startswith("powershell"):
+            return await asyncio.create_subprocess_shell(command, **kwargs)
         bash = find_bash()
         if bash:
             return await asyncio.create_subprocess_exec(bash, "-c", command, **kwargs)
@@ -672,8 +677,8 @@ async def _generate_win_detached(cmd: str, request: Request):
     if bash:
         script_path = TMUX_LOG_DIR / f"{session_id}.sh"
         script_path.write_text(
-            f"{cmd} > {shlex.quote(str(log_path))} 2>&1\n"
-            f"echo $? > {shlex.quote(str(exit_path))}\n",
+            f"{cmd} > {shlex.quote(git_bash_path(log_path))} 2>&1\n"
+            f"echo $? > {shlex.quote(git_bash_path(exit_path))}\n",
             encoding="utf-8",
         )
         argv = [bash, str(script_path)]