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/screenshot/to_file.lua

@@ -0,0 +1,36 @@
+-- Capture full screen → save PNG under ~/Pictures/Screenshots/jarvis-YYYYMMDD-HHMMSS.png
+local t = jarvis.context.time
+local stamp = string.format("%04d%02d%02d-%02d%02d%02d",
+    t.year, t.month, t.day, t.hour, t.minute, t.second or 0)
+
+local userprofile = jarvis.system.env("USERPROFILE") or "C:\\Users\\Public"
+local dir = userprofile .. "\\Pictures\\Screenshots"
+local path = string.format("%s\\jarvis-%s.png", dir, stamp)
+
+-- Ensure dir exists
+jarvis.fs.mkdir(dir)
+
+local escaped = path:gsub("'", "''")
+local ps = string.format([[
+Add-Type -AssemblyName System.Windows.Forms
+Add-Type -AssemblyName System.Drawing
+$bounds = [System.Windows.Forms.Screen]::PrimaryScreen.Bounds
+$bmp = New-Object System.Drawing.Bitmap $bounds.Width, $bounds.Height
+$g = [System.Drawing.Graphics]::FromImage($bmp)
+$g.CopyFromScreen($bounds.Location, [System.Drawing.Point]::Empty, $bounds.Size)
+$bmp.Save('%s', [System.Drawing.Imaging.ImageFormat]::Png)
+$g.Dispose(); $bmp.Dispose()
+]], escaped)
+
+local res = jarvis.system.exec(string.format(
+    'powershell -NoProfile -ExecutionPolicy Bypass -Command "%s"',
+    ps:gsub('"', '\\"'):gsub("\r?\n", "; ")
+))
+
+if not res.success then
+    jarvis.log("warn", "screenshot to file failed: " .. tostring(res.stderr):sub(1, 200))
+    return jarvis.cmd.error("Не получилось сохранить скриншот.")
+end
+
+jarvis.system.notify("Скриншот", path)
+return jarvis.cmd.ok("Скриншот сохранён в папку Скриншоты.")