feat(commands): add PC control packs — volume, apps, file_search, output_device

All four packs are pure Lua (sandbox=full) and call out to PowerShell helpers
where COM / native APIs are needed. No new Rust code, no rebuild required:
post_build.py --sync copies them under target/{debug,release}/resources/.

volume/
  - volume_up / volume_down: 5x VK_VOLUME_UP|DOWN via keybd_event
  - volume_mute: VK_VOLUME_MUTE
  - volume_max: 50x VK_VOLUME_UP (system clamps)
  Helper _volume_helper.ps1 P/Invokes user32!keybd_event.

apps/
  - open_browser  : start "" https://www.google.com (uses system default browser)
  - open_notepad  : notepad.exe
  - open_calculator: calc.exe
  - open_explorer : explorer.exe
  - open_terminal : wt.exe, falls back to powershell.exe
  - open_settings : ms-settings: protocol
  - open_task_manager: taskmgr.exe
  - lock_screen   : rundll32 user32.dll,LockWorkStation
  - screenshot    : System.Drawing capture to ~/Pictures/jarvis_screenshot_*.png

file_search/
  - find file <query> : recursive Get-ChildItem in Desktop/Documents/Downloads
    (depth 3, top 5 matches). Strips Russian/English/Ukrainian trigger
    prefixes from the recognized phrase, then opens explorer /select on the
    first hit and notifies with the total count.

output_device/
  - list_output_devices : enumerates active render endpoints via
    IMMDeviceEnumerator and notifies friendly names with indices
  - next_output_device  : cycles the system default render device via the
    undocumented IPolicyConfig::SetDefaultEndpoint (eConsole/Multimedia/
    Communications). Tested locally — listed 7 devices, current correctly
    identified at index 5.

resources/commands/file_search/search.lua

@@ -0,0 +1,78 @@
+local lang = jarvis.context.language
+local phrase = (jarvis.context.phrase or ""):lower()
+
+local triggers = {
+    "найди документ", "найди файл", "поиск файла", "ищи файл", "где файл",
+    "find file", "search file", "where is file", "locate file",
+    "знайди файл", "пошук файлу", "де файл",
+}
+
+local query = phrase
+for _, t in ipairs(triggers) do
+    local start, finish = string.find(query, t, 1, true)
+    if start == 1 then
+        query = query:sub(finish + 1)
+        break
+    end
+end
+query = query:gsub("^%s+", ""):gsub("%s+$", "")
+
+if query == "" then
+    jarvis.log("warn", "file_search: empty query (phrase=" .. phrase .. ")")
+    jarvis.system.notify(
+        lang == "ru" and "Поиск файлов" or "File search",
+        lang == "ru" and "Что искать?" or "What to search for?"
+    )
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local userprofile = jarvis.system.env("USERPROFILE") or "C:\\Users\\Public"
+local roots = {
+    userprofile .. "\\Desktop",
+    userprofile .. "\\Documents",
+    userprofile .. "\\Downloads",
+}
+
+local escaped = query:gsub("'", "''")
+local roots_arg = "'" .. table.concat(roots, "','") .. "'"
+local ps = string.format(
+    [[$ErrorActionPreference='SilentlyContinue'; $r=@(%s); $q='*%s*'; $hits=Get-ChildItem -Path $r -Filter $q -Recurse -Depth 3 -File | Select-Object -First 5; foreach($h in $hits){ Write-Output $h.FullName }]],
+    roots_arg, escaped
+)
+
+local cmd = string.format('powershell -NoProfile -ExecutionPolicy Bypass -Command "%s"', ps:gsub('"', '\\"'))
+jarvis.log("info", "file_search query='" .. query .. "'")
+
+local res = jarvis.system.exec(cmd)
+
+if not res.success then
+    jarvis.log("error", "file_search exec failed: " .. tostring(res.stderr))
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local stdout = res.stdout or ""
+local lines = {}
+for line in stdout:gmatch("[^\r\n]+") do
+    if line ~= "" then table.insert(lines, line) end
+end
+
+if #lines == 0 then
+    jarvis.system.notify(
+        lang == "ru" and "Поиск файлов" or "File search",
+        (lang == "ru" and "Не найдено: " or "Not found: ") .. query
+    )
+    jarvis.audio.play_not_found()
+else
+    local first = lines[1]
+    local count = #lines
+    local title = lang == "ru" and "Найдено файлов: " or "Files found: "
+    jarvis.system.notify(title .. count, first)
+
+    jarvis.log("info", "file_search opening: " .. first)
+    jarvis.system.exec(string.format('explorer.exe /select,"%s"', first))
+    jarvis.audio.play_ok()
+end
+
+return { chain = false }