feat: WSL support, js-yaml migration, and stability improvements

- PID/log files moved to ~/.hermes-web-ui/ for WSL compatibility
- Replace all regex YAML parsing with js-yaml in filesystem.ts
- Auto-detect WSL and use hermes gateway run for background startup
- Stop command: SIGTERM with SIGKILL fallback, clean stale PIDs
- Setup script: auto-install Node.js and hermes-web-ui

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/services/hermes-cli.ts

@@ -182,7 +182,7 @@ export async function getVersion(): Promise<string> {
 }
 
 /**
- * Start Hermes gateway
+ * Start Hermes gateway (uses launchd/systemd)
  */
 export async function startGateway(): Promise<string> {
   const { stdout, stderr } = await execFileAsync('hermes', ['gateway', 'start'], {
@@ -191,6 +191,20 @@ export async function startGateway(): Promise<string> {
   return stdout || stderr
 }
 
+/**
+ * Start Hermes gateway in background (for WSL where launchd/systemd is unavailable)
+ * Uses "hermes gateway run" as a detached background process
+ */
+export async function startGatewayBackground(): Promise<number | null> {
+  const { spawn } = require('child_process') as typeof import('child_process')
+  const child = spawn('hermes', ['gateway', 'run'], {
+    detached: true,
+    stdio: 'ignore',
+  })
+  child.unref()
+  return child.pid ?? null
+}
+
 /**
  * Restart Hermes gateway
  */