feat(39-02): voice capability probe in hardware service

- Add VoiceCapability interface with whisperAvailable, piperAvailable, voiceTierSufficient
- Extend HardwareInfo with voiceCapability field
- Add detectVoiceCapability() probing whisper-cpp/whisper and piper with 2s timeout each
- voiceTierSufficient: true for apple_silicon/gpu, or cpu_only with >= 4GB free RAM
- Wrap voice probe in 3s timeout to avoid slowing hardware detection
- Route automatically includes voiceCapability via existing HardwareInfo return

server/src/services/hardware.ts

@@ -1,8 +1,16 @@
 import os from "node:os";
+import { execFile as execFileCb } from "node:child_process";
 import si from "systeminformation";
 
 export type HardwareTier = "gpu" | "apple_silicon" | "cpu_only";
 
+export interface VoiceCapability {
+  whisperAvailable: boolean;
+  piperAvailable: boolean;
+  /** true if hardware tier >= apple_silicon OR (cpu_only with >= 4GB free RAM) */
+  voiceTierSufficient: boolean;
+}
+
 export interface HardwareInfo {
   totalGb: number;
   freeGb: number;
@@ -13,6 +21,7 @@ export interface HardwareInfo {
   unifiedMemory: boolean;
   hardwareTier: HardwareTier;
   cpuModel: string | null;
+  voiceCapability: VoiceCapability;
 }
 
 const CACHE_TTL_MS = 5 * 60 * 1000; // 5 minutes
@@ -26,6 +35,63 @@ export function _resetHardwareCache(): void {
   cacheExpiry = 0;
 }
 
+/** Promisified execFile wrapper for consistent mocking in tests. */
+function execFileAsync(
+  cmd: string,
+  args: string[],
+  opts: { timeout?: number }
+): Promise<{ stdout: string; stderr: string }> {
+  return new Promise((resolve, reject) => {
+    execFileCb(cmd, args, opts as never, (err, stdout, stderr) => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve({
+          stdout: Buffer.isBuffer(stdout) ? stdout.toString() : String(stdout ?? ""),
+          stderr: Buffer.isBuffer(stderr) ? stderr.toString() : String(stderr ?? ""),
+        });
+      }
+    });
+  });
+}
+
+/** Probe for Whisper and Piper binary availability. */
+async function detectVoiceCapability(
+  hardwareTier: HardwareTier,
+  freeGb: number
+): Promise<VoiceCapability> {
+  // Probe whisper-cpp first, fall back to whisper (openai-whisper)
+  let whisperAvailable = false;
+  try {
+    await execFileAsync("whisper-cpp", ["--help"], { timeout: 2000 });
+    whisperAvailable = true;
+  } catch {
+    try {
+      await execFileAsync("whisper", ["--help"], { timeout: 2000 });
+      whisperAvailable = true;
+    } catch {
+      whisperAvailable = false;
+    }
+  }
+
+  // Probe piper
+  let piperAvailable = false;
+  try {
+    await execFileAsync("piper", ["--help"], { timeout: 2000 });
+    piperAvailable = true;
+  } catch {
+    piperAvailable = false;
+  }
+
+  // voiceTierSufficient: true for apple_silicon/gpu, or cpu_only with >= 4GB free
+  const voiceTierSufficient =
+    hardwareTier === "apple_silicon" ||
+    hardwareTier === "gpu" ||
+    (hardwareTier === "cpu_only" && freeGb >= 4);
+
+  return { whisperAvailable, piperAvailable, voiceTierSufficient };
+}
+
 export function hardwareService() {
   async function detect(): Promise<HardwareInfo> {
     const now = Date.now();
@@ -43,6 +109,9 @@ export function hardwareService() {
 
     // Apple Silicon detection: darwin platform + CPU brand starting with "Apple"
     if (platform === "darwin" && cpuModel?.startsWith("Apple")) {
+      const voiceCapability = await withVoiceTimeout(
+        detectVoiceCapability("apple_silicon", freeGb)
+      );
       const info: HardwareInfo = {
         totalGb,
         freeGb,
@@ -53,6 +122,7 @@ export function hardwareService() {
         unifiedMemory: true,
         hardwareTier: "apple_silicon",
         cpuModel,
+        voiceCapability,
       };
       cache = info;
       cacheExpiry = now + CACHE_TTL_MS;
@@ -84,6 +154,10 @@ export function hardwareService() {
       hardwareTier = "cpu_only";
     }
 
+    const voiceCapability = await withVoiceTimeout(
+      detectVoiceCapability(hardwareTier, freeGb)
+    );
+
     const info: HardwareInfo = {
       totalGb,
       freeGb,
@@ -94,6 +168,7 @@ export function hardwareService() {
       unifiedMemory: false,
       hardwareTier,
       cpuModel,
+      voiceCapability,
     };
 
     cache = info;
@@ -103,3 +178,16 @@ export function hardwareService() {
 
   return { detect };
 }
+
+/** Wrap voice capability probe with 3s timeout; return safe defaults on failure. */
+async function withVoiceTimeout(
+  probe: Promise<VoiceCapability>
+): Promise<VoiceCapability> {
+  const timeout = new Promise<VoiceCapability>((resolve) =>
+    setTimeout(
+      () => resolve({ whisperAvailable: false, piperAvailable: false, voiceTierSufficient: false }),
+      3000
+    )
+  );
+  return Promise.race([probe, timeout]);
+}