Installer fails on valid Debian 12 NAS environment (PATH, HOME and CPU instruction handling)

Environment
OS: Debian 12 (Bookworm)
Distribution: FNOS (Debian-based NAS)
Architecture: x86_64
CPU: Intel Celeron J4105
GPU: NVIDIA GPU installed (CUDA capable)
llmster version: 0.0.18-1
Summary

First of all, thank you for making LM Studio and llmster available for Linux. I really appreciate the work that has gone into this project.

While testing llmster on a Debian 12 based NAS system (FNOS), I encountered several installer/runtime issues. None of them are difficult to work around individually, but together they make installation fail on an otherwise valid Linux system.

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### Issue 1 - Installer assumes ldconfig is in PATH

The installer exits with:

ERROR: "ldconfig" must be available on your PATH before installing.

On Debian-based NAS systems, ldconfig exists at:

/usr/sbin/ldconfig

but /usr/sbin is intentionally not included in a normal user's PATH.

The installer could either:

search common locations (/usr/sbin, /sbin)
invoke ldconfig by absolute path
or print a suggestion to temporarily extend PATH.

---

### Issue 2 - Installer crashes when HOME directory does not exist

My user account has:

HOME=/home/XXX

and /etc/passwd also points to /home/XXX.

However, this NAS platform intentionally does not create that directory because user data is managed elsewhere.

The installer crashes with:

ENOENT: no such file or directory
lstat '/home/XXX'

Creating /home/XXX manually allows the installation to continue.

Instead of crashing, it would be nice if the installer:

created the HOME directory when appropriate,
or displayed a friendly error message explaining the problem.

---

### Issue 3 - No CPU capability check

Installation finishes successfully, but running:

lms

or

lms --version

immediately results in:

Illegal instruction

The CPU is an Intel Celeron J4105, which supports SSE4.2 but does not support AVX/AVX2.

It would be helpful if the installer (or launcher) detected unsupported CPU instruction sets and reported something like:

The binary immediately exits with Illegal instruction (SIGILL) on a Celeron J4105 (no AVX/AVX2 support). If newer instruction sets are required, a compatibility check with a clear error message would greatly improve the user experience.

instead of crashing with SIGILL.

Expected behavior

The installer should gracefully handle:

Debian systems where /usr/sbin is not in PATH
HOME directories that are referenced but not yet created
CPUs without AVX2 by reporting a clear compatibility message

These changes would improve compatibility with NAS devices and other embedded Linux systems.

Thanks again for your work on LM Studio and llmster.

Start by reproducing installation and lms --version on Debian 12/FNOS, focusing on the installer and launcher paths described in the report. Verify handling for /usr/sbin/ldconfig, a missing HOME directory, and CPUs without AVX2; done means each case produces a graceful, clear outcome instead of installation failure or SIGILL.