feat(kon): add core crate — types, traits, hardware, model registry, recommendation

- Value objects: ModelId, EngineName, Megabytes, AudioSamples, Segment, Transcript
- KonError enum with thiserror
- Constants centralised: audio pipeline, VAD, RAM thresholds, inference threading
- SpeechToText and TextProcessor provider traits with ProviderRegistry
- Unified model registry (Whisper tiny/base/small/medium + Parakeet CTC int8)
- Hardware detection: probe_ram, probe_cpu, probe_gpu (stub), probe_os
- Recommendation engine: score_model (pure function), rank_recommendations (sorted)
- 5 tests passing, clippy clean

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/core/src/hardware.rs

@@ -0,0 +1,107 @@
+use sysinfo::System;
+
+use crate::types::Megabytes;
+
+/// Detected system capabilities.
+#[derive(Debug, Clone)]
+pub struct SystemProfile {
+    pub ram: Megabytes,
+    pub cpu: CpuInfo,
+    pub gpu: Option<GpuInfo>,
+    pub os: Os,
+}
+
+#[derive(Debug, Clone)]
+pub struct CpuInfo {
+    pub core_count: usize,
+    pub brand: String,
+}
+
+#[derive(Debug, Clone)]
+pub struct GpuInfo {
+    pub vendor: GpuVendor,
+    pub vram: Megabytes,
+    pub acceleration: GpuAcceleration,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum GpuVendor {
+    Nvidia,
+    Amd,
+    Intel,
+    Apple,
+    Unknown,
+}
+
+#[derive(Debug, Clone)]
+pub struct GpuAcceleration {
+    pub cuda: bool,
+    pub metal: bool,
+    pub vulkan: bool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Os {
+    Windows,
+    Linux,
+    MacOs,
+    Ios,
+    Android,
+}
+
+pub fn probe_ram() -> Megabytes {
+    let sys = System::new_all();
+    let total_bytes = sys.total_memory();
+    Megabytes(total_bytes / (1024 * 1024))
+}
+
+pub fn probe_cpu() -> CpuInfo {
+    let sys = System::new_all();
+    CpuInfo {
+        core_count: sys.cpus().len(),
+        brand: sys
+            .cpus()
+            .first()
+            .map(|c| c.brand().to_string())
+            .unwrap_or_default(),
+    }
+}
+
+pub fn probe_gpu() -> Option<GpuInfo> {
+    // GPU detection via wgpu or platform-specific APIs.
+    // Placeholder: returns None until wgpu or nvml integration is added.
+    None
+}
+
+pub fn probe_os() -> Os {
+    #[cfg(target_os = "windows")]
+    {
+        Os::Windows
+    }
+    #[cfg(target_os = "linux")]
+    {
+        Os::Linux
+    }
+    #[cfg(target_os = "macos")]
+    {
+        Os::MacOs
+    }
+    #[cfg(target_os = "ios")]
+    {
+        Os::Ios
+    }
+    #[cfg(target_os = "android")]
+    {
+        Os::Android
+    }
+}
+
+/// Composes the individual probes. No logic here — just assembly.
+pub fn probe_system() -> SystemProfile {
+    SystemProfile {
+        ram: probe_ram(),
+        cpu: probe_cpu(),
+        gpu: probe_gpu(),
+        os: probe_os(),
+    }
+}