fix(detection): add sysctl hw.ncpu lookup on macOS in detection.sh

[vaibhavsrv]

Problem

In ods/installers/lib/detection.sh, get_host_logical_cpus() resolves system CPU core count using nproc 2>/dev/null || grep -c ^processor /proc/cpuinfo. On macOS (Darwin), neither nproc nor /proc/cpuinfo exist by default, causing get_host_logical_cpus() to fall back to 1 core. This led to under-allocated thread counts (--threads 1) during llama-server CPU thread budget calculation on Apple Silicon Macs.

Fix

Add sysctl -n hw.ncpu 2>/dev/null as the primary hardware query in get_host_logical_cpus() in detection.sh.

Verification

Ran bash -n ods/installers/lib/detection.sh (passed cleanly). Verified CPU core count resolution on macOS. git diff --check passed cleanly.