feat: lock_workstation + screenshot + net_info packs + modernise power pack

Three handy daily-driver packs + cleanup of the oldest power/act.lua.

power pack — added lock_workstation (resources/commands/power/)
  - New command id: lock_workstation
  - Phrase: "заблокируй компьютер" / "заблокируй пк" / "заблокируй экран"
  - Action: rundll32.exe user32.dll,LockWorkStation
  - Sandbox: full (needs system.exec)
  - act.lua modernised:
    * No more inline PowerShell SAPI escape chain — now uses jarvis.speak
      (TTS backend abstraction respects user's chosen Piper/SAPI/Silero).
    * Returns via jarvis.cmd.ok/error helpers.
    * Logged warning for failing cmds without crashing the pack.
    * Cleaner per-action `warn` flag controls the "say cancel to abort" hint.

screenshot pack (NEW, resources/commands/screenshot/, 2 commands)
  - "сделай скрин" / "сделай скриншот" → screenshot.to_clipboard
    Uses [System.Windows.Forms.Clipboard]::SetImage() with a captured Bitmap.
    No file artifact, no LLM call — pure capture, fastest path.
  - "сохрани скрин" → screenshot.to_file
    Saves to ~/Pictures/Screenshots/jarvis-YYYYMMDD-HHMMSS.png.
    Creates dir if missing. Notifies with full path.
  - Distinct from vision/ pack which captures + describes via LLM.

net_info pack (NEW, resources/commands/net_info/, 3 commands)
  - "какая сеть" / "какой wifi" → net.wifi_ssid
    Parses `netsh wlan show interfaces` for SSID line (RU + EN field names).
  - "мой IP" / "локальный IP" → net.local_ip
    PowerShell Get-NetIPAddress, filters out 127.* and 169.* (link-local).
  - "внешний IP" / "публичный IP" → net.public_ip
    Hits api.ipify.org via jarvis.http.get (no key, plain text).

Tests: 99/99 pass (commands::tests auto-validates new packs).
Build: cargo build --release -p jarvis-app green.

Pack count: 59 → 62 (intro/echo from prior commit + screenshot + net_info; power
already counted — added a command, not a pack).

resources/commands/net_info/wifi.lua

@@ -0,0 +1,18 @@
+-- "Какая сеть" → `netsh wlan show interfaces` → grep SSID
+local res = jarvis.system.exec('netsh wlan show interfaces')
+if not res.success then
+    return jarvis.cmd.error("Не получилось получить данные о Wi-Fi.")
+end
+
+local out = res.stdout or ""
+local ssid = out:match("SSID%s+:%s+(.-)\r?\n")
+-- Russian Windows: "SSID                   : MyNetwork"
+-- The non-localised case: same format
+if not ssid then ssid = out:match("Имя сети%s+:%s+(.-)\r?\n") end
+ssid = ssid and ssid:gsub("^%s+", ""):gsub("%s+$", "") or ""
+
+if ssid == "" or ssid == "(нет)" or ssid == "(none)" then
+    return jarvis.cmd.not_found("Wi-Fi не подключен или адаптер выключен.")
+end
+
+return jarvis.cmd.ok("Сеть: " .. ssid .. ".")