r006: Add unraid_system_shell tool (direct terminal access)

- New helper runShell(): executes /bin/sh -c, returns {exit_code, stdout, stderr} as JSON
- New tool unraid_system_shell: direct shell access on Unraid host (root)
  - params: command (required), timeout_seconds (1-300, default 60)
  - output size-limited via sanitizeLogOutput
- Version bump r005 -> r006

src/helpers.ts

@@ -13,7 +13,7 @@ import { createConnection, type Socket } from "net";
 
 // ── Konstanten ──────────────────────────────────────────────────────────
 export const MUA_SERVER_NAME = "mua";
-export const MUA_VERSION = "2026.08.18.r005";
+export const MUA_VERSION = "2026.08.18.r006";
 export const MUA_PROTOCOL_VERSION = "2025-03-26";
 export const PHP_HELPER = "/usr/local/bin/unraid-docker-mcp-helper.php";
 
@@ -53,6 +53,34 @@ export async function runLocal(
   }
 }
 
+/**
+ * Shell-Befehl ausführen und strukturiertes Ergebnis liefern
+ * (exit_code + stdout + stderr). Für das unraid_system_shell-Tool.
+ * Liefert JSON, damit der Agent Exit-Code und beides Streams sieht.
+ */
+export async function runShell(cmd: string, timeoutSec = 60): Promise<string> {
+  try {
+    const proc = spawn(["/bin/sh", "-c", cmd], {
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const timeout = setTimeout(() => proc.kill(), timeoutSec * 1000);
+    const [stdout, stderr, code] = await Promise.all([
+      new Response(proc.stdout).text(),
+      new Response(proc.stderr).text(),
+      proc.exited,
+    ]);
+    clearTimeout(timeout);
+    return JSON.stringify({
+      exit_code: code,
+      stdout: sanitizeLogOutput(stdout.trim(), 100000),
+      stderr: sanitizeLogOutput(stderr.trim(), 20000),
+    });
+  } catch (e) {
+    throw new Error(`run_shell failed: ${String(e)}`);
+  }
+}
+
 /**
  * Docker-Befehl ausführen (kompakt).
  */