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/codegen/codegen.lua

@@ -0,0 +1,99 @@
+local lang = jarvis.context.language
+local phrase = (jarvis.context.phrase or ""):lower()
+
+local triggers = {
+    "сгенерируй скрипт", "напиши скрипт", "сделай скрипт",
+    "сгенерируй код", "набросай код", "напиши код",
+    "generate code", "write code", "make script", "write script",
+    "згенеруй код", "напиши код", "зроби скрипт",
+}
+
+local request = phrase
+for _, t in ipairs(triggers) do
+    local s, e = string.find(request, t, 1, true)
+    if s == 1 then
+        request = request:sub(e + 1)
+        break
+    end
+end
+request = request:gsub("^%s+", ""):gsub("%s+$", "")
+
+if request == "" then
+    jarvis.system.notify(
+        lang == "ru" and "Codegen" or "Codegen",
+        lang == "ru" and "Что писать?" or "What to write?"
+    )
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local token = jarvis.system.env("GROQ_TOKEN")
+if not token or token == "" then
+    jarvis.log("error", "GROQ_TOKEN not set")
+    jarvis.system.notify("Codegen", "GROQ_TOKEN не задан")
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local base = jarvis.system.env("GROQ_BASE_URL")
+if not base or base == "" then base = "https://api.groq.com/openai/v1" end
+
+local model = jarvis.system.env("GROQ_MODEL")
+if not model or model == "" then model = "llama-3.3-70b-versatile" end
+
+local system_prompt = lang == "ru"
+    and "Ты Senior Engineer. На запрос пользователя верни ТОЛЬКО исходный код, без обрамления ``` и без объяснений. Если язык не задан — выбери самый подходящий (по умолчанию Python). Не добавляй комментарии-болтовню."
+    or "You are a Senior Engineer. Reply with ONLY source code, no ``` fences, no commentary. Pick the most fitting language if unspecified (Python by default). Skip chatty comments."
+
+jarvis.log("info", "codegen request: " .. request)
+
+local payload = {
+    model = model,
+    messages = {
+        { role = "system", content = system_prompt },
+        { role = "user",   content = request },
+    },
+    max_tokens = 1024,
+    temperature = 0.2,
+}
+
+local headers = { Authorization = "Bearer " .. token }
+local res = jarvis.http.post_json(base .. "/chat/completions", payload, headers)
+
+if not res.ok then
+    jarvis.log("error", "codegen API failed: status=" .. tostring(res.status) .. " body=" .. tostring(res.body):sub(1, 200))
+    jarvis.system.notify("Codegen", "Ошибка API: " .. tostring(res.status))
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+local body = res.body or ""
+local content = body:match('"content"%s*:%s*"(.-[^\\])"')
+if not content then
+    jarvis.log("error", "codegen: could not parse content from " .. body:sub(1, 200))
+    jarvis.system.notify("Codegen", "Не смог распарсить ответ")
+    jarvis.audio.play_error()
+    return { chain = false }
+end
+
+content = content:gsub('\\n', '\n')
+content = content:gsub('\\"', '"')
+content = content:gsub('\\\\', '\\')
+content = content:gsub('\\t', '\t')
+
+content = content:gsub("^```[%w]*\n?", "")
+content = content:gsub("\n?```%s*$", "")
+content = content:gsub("^%s+", ""):gsub("%s+$", "")
+
+jarvis.system.clipboard.set(content)
+jarvis.log("info", "codegen result copied to clipboard (" .. #content .. " bytes)")
+
+local preview = content:sub(1, 120)
+if #content > 120 then preview = preview .. "..." end
+jarvis.system.notify(
+    lang == "ru" and "Код в буфере" or "Code in clipboard",
+    preview
+)
+jarvis.audio.play_ok()
+
+return { chain = false }