feat: LLM auto-fallback + codegen pack + OCR pack

LLM auto-fallback (jarvis-app/src/app.rs + jarvis-core/src/config.rs):
- When neither intent classifier nor levenshtein finds a command match,
  route the utterance straight to the LLM instead of just playing the
  "not found" sound. Triggers ("скажи X", "answer Y") still work and
  take precedence — they short-circuit before command lookup.
- Two new config knobs:
    LLM_AUTO_FALLBACK = true        — master toggle
    LLM_AUTO_FALLBACK_MIN_CHARS = 4 — suppress for very short utterances
                                       so background noise doesn't burn
                                       Groq quota
- Requires GROQ_TOKEN; if absent, behaviour is unchanged (play_not_found).

codegen/ command pack:
- Phrases: "напиши код X", "сгенерируй скрипт Y", "write code Z", etc.
- Strips the trigger from the recognized phrase, sends what remains to
  Groq with a strict system prompt ("return ONLY code, no fences, no
  commentary") at temperature 0.2.
- Parses the JSON content, unescapes \n / \" / \\ / \t, strips any
  remaining ```lang ... ``` fences, drops the result into the clipboard
  via jarvis.system.clipboard.set.
- Notifies a 120-char preview + plays ok-sound. Works for any language
  the model handles (Python by default if unspecified).
- GROQ_TOKEN / GROQ_MODEL / GROQ_BASE_URL read from env at call time —
  same envvars the voice-loop fallback already uses.

ocr/ command pack:
- Phrases: "прочитай экран", "что на экране", "read screen", etc.
- Captures the primary screen via System.Windows.Forms + System.Drawing
  to a temp PNG, then shells to tesseract.exe (-l rus+eng for ru/ua,
  -l eng for en).
- Resolves Tesseract by PATH first, then C:\Program Files\Tesseract-OCR
  and the x86 install dir; if none works the user gets a friendly
  "winget install UB-Mannheim.TesseractOCR" hint in a notification.
- Recognized text goes to clipboard + a 200-char preview notification.

All three features are portable (env-var resolution, no hardcoded user
paths). Command-pack total is now 11. cargo test -p jarvis-core --lib
commands::tests passes 3/3.

resources/commands/ocr/read_screen.lua

@@ -0,0 +1,82 @@
+local lang = jarvis.context.language
+
+local temp = jarvis.system.env("TEMP") or jarvis.system.env("TMP") or "C:\\Windows\\Temp"
+local ts = jarvis.context.time.year .. jarvis.context.time.month .. jarvis.context.time.day
+    .. "_" .. jarvis.context.time.hour .. jarvis.context.time.minute .. jarvis.context.time.second
+local img = temp .. "\\jarvis_ocr_" .. ts .. ".png"
+
+local capture_ps = string.format(
+    [[Add-Type -AssemblyName System.Windows.Forms,System.Drawing; $b=[System.Windows.Forms.Screen]::PrimaryScreen.Bounds; $bmp=New-Object Drawing.Bitmap $b.Width,$b.Height; $g=[Drawing.Graphics]::FromImage($bmp); $g.CopyFromScreen($b.Location,[Drawing.Point]::Empty,$b.Size); $bmp.Save('%s'); $g.Dispose(); $bmp.Dispose()]],
+    img:gsub("\\", "\\\\")
+)
+local capture_cmd = string.format('powershell -NoProfile -ExecutionPolicy Bypass -Command "%s"', capture_ps:gsub('"', '\\"'))
+local cap = jarvis.system.exec(capture_cmd)
+
+if not cap.success or not jarvis.fs.exists(img) then
+    jarvis.log("error", "screen capture failed: " .. tostring(cap.stderr))
+    jarvis.system.notify("OCR", lang == "ru" and "Не смог снять экран" or "Could not capture screen")
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local tesseract_paths = {
+    "tesseract.exe",
+    "C:\\Program Files\\Tesseract-OCR\\tesseract.exe",
+    "C:\\Program Files (x86)\\Tesseract-OCR\\tesseract.exe",
+}
+
+local tess = nil
+for _, p in ipairs(tesseract_paths) do
+    local check
+    if p == "tesseract.exe" then
+        check = jarvis.system.exec("where tesseract.exe")
+    else
+        check = { success = jarvis.fs.exists(p), stdout = p }
+    end
+    if check.success and (check.stdout or ""):gsub("[\r\n]+$", "") ~= "" then
+        tess = p == "tesseract.exe" and "tesseract.exe" or '"' .. p .. '"'
+        break
+    end
+end
+
+if not tess then
+    jarvis.log("error", "tesseract not found")
+    jarvis.system.notify(
+        "OCR",
+        lang == "ru"
+            and "Tesseract не установлен. Установи: winget install UB-Mannheim.TesseractOCR"
+            or "Tesseract not installed. Install: winget install UB-Mannheim.TesseractOCR"
+    )
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local langs = lang == "en" and "eng" or "rus+eng"
+local ocr_cmd = string.format('%s "%s" - -l %s', tess, img, langs)
+local ocr = jarvis.system.exec(ocr_cmd)
+
+if not ocr.success then
+    jarvis.log("error", "tesseract failed: " .. tostring(ocr.stderr):sub(1, 200))
+    jarvis.system.notify("OCR", lang == "ru" and "Tesseract упал" or "Tesseract failed")
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local text = (ocr.stdout or ""):gsub("^%s+", ""):gsub("%s+$", "")
+if text == "" then
+    jarvis.system.notify("OCR", lang == "ru" and "Текста не найдено" or "No text found")
+    jarvis.audio.play_not_found()
+    return { chain = false }
+end
+
+jarvis.system.clipboard.set(text)
+jarvis.log("info", "OCR result (" .. #text .. " bytes) copied to clipboard")
+
+local preview = text:gsub("\r?\n", " "):sub(1, 200)
+if #text > 200 then preview = preview .. "..." end
+jarvis.system.notify(
+    lang == "ru" and "Текст с экрана" or "Screen text",
+    preview
+)
+jarvis.audio.play_ok()
+return { chain = false }