feat: TTS backend abstraction + 4 'imba' features + Lua packs

Big push driven by user feedback ("делай имбу") and web research on what
voice assistants need to be the ideal:

TTS backend abstraction (P0.1)
  - new module crates/jarvis-core/src/tts/{mod,sapi,piper,silero}.rs
  - TtsBackend trait with SapiBackend (current PowerShell), PiperBackend
    (rhasspy/piper, neural quality), SileroBackend (python subprocess)
  - JARVIS_TTS env var picks (sapi|piper|silero). Auto-detect Piper if
    binary + voice present in tools/piper/. Falls back to SAPI on missing.
  - SpeakOpts {lang, detached, raw} replaces ad-hoc args. text_utils
    sanitiser applied unless raw=true.
  - llm_fallback + lua/api/tts both routed through tts::backend().
  - tools/piper/install.ps1 downloads piper.exe + ru_RU-irina-medium.onnx
    from rhasspy releases + huggingface. Smoke-test included.
  - tools/silero/silero_tts.py helper (PyTorch); rust spawns it as subprocess.

IMBA-1 Agentic LLM router
  - crates/jarvis-app/src/llm_router.rs
  - When fuzzy/intent matcher fails, LLM picks the closest command from the
    full registry. Returns JSON {command_id, confidence, reason}.
  - Threshold-gated re-dispatch via substitute phrase. JARVIS_LLM_ROUTER=1
    enables; JARVIS_LLM_ROUTER_THRESHOLD overrides 0.55 default.
  - Inserted in app.rs::execute_command between "no match" and existing
    llm_fallback chat fallback.

IMBA-2 Long-term memory
  - crates/jarvis-core/src/long_term_memory.rs — JSON store at
    APP_CONFIG_DIR/long_term_memory.json. Atomic write-through.
  - remember/recall/search/forget/all/build_context API.
  - Lua bindings: jarvis.memory.* (5 functions).
  - llm_fallback auto-injects relevant facts (substring search of prompt)
    into system message before LLM call.
  - Pack resources/commands/memory_pack/ with 4 commands: remember, recall,
    forget, list.

IMBA-3 Profile switching (work/game/sleep/driving/default)
  - crates/jarvis-core/src/profiles.rs — JSON profiles at APP_CONFIG_DIR/profiles/
    Auto-seeds 5 defaults on first run with personality + allow/deny lists +
    greetings + emoji icons.
  - active_profile.txt persists choice across restart.
  - Lua bindings: jarvis.profile.{active,set,list,allows,active_name}.
  - llm_fallback prepends profile personality to system prompt.
  - Pack resources/commands/profile_switch/ with 6 voice triggers.

IMBA-4 Multimodal screenshot + vision LLM
  - crates/jarvis-core/src/lua/api/vision.rs — gated on HTTP sandbox.
  - jarvis.vision.screenshot() captures via PowerShell System.Drawing.
  - jarvis.vision.describe(prompt?) sends base64 PNG to Groq vision model
    (default llama-3.2-11b-vision-preview, override via GROQ_VISION_MODEL).
  - Pack resources/commands/vision/ with 2 commands: describe + read_error.

P0.2 Continuous conversation grace window
  - config::CONVERSATION_GRACE_MS = 30_000.
  - app.rs: after command result, if grace_ms > 0 keep listening WITHOUT
    re-wake for the grace duration. Existing CMS_WAIT_DELAY back-dated so
    the existing timeout fires at start + grace_ms.

Tests: 24/24 jarvis-core unit tests pass (including 5 text_utils).
Build: cargo build --release -p jarvis-app and -p jarvis-gui both succeed
on Windows MSVC (VS 2026 Enterprise vcvars64).

Notes for setup:
  - Piper voice install: pwsh tools/piper/install.ps1 (downloads ~90 MB).
  - GROQ_TOKEN needed for IMBA-1 (router) and IMBA-4 (vision).
  - All features are opt-in via env vars or auto-detect; existing SAPI +
    fuzzy match path remains the default.

tools/piper/README.md

@@ -0,0 +1,64 @@
+# Piper TTS (neural voice for J.A.R.V.I.S.)
+
+Drop-in replacement for the robotic SAPI voice. ~30 MB binary + ~60 MB Russian voice (Irina). Latency 200-500ms on i5.
+
+## Install
+
+```powershell
+cd C:\Jarvis\rust\tools\piper
+pwsh -File install.ps1
+```
+
+By default installs `ru_RU-irina-medium` (Russian female). To pick a different voice:
+
+```powershell
+pwsh -File install.ps1 -Voice ru_RU-denis-medium
+pwsh -File install.ps1 -Voice ru_RU-dmitri-medium
+pwsh -File install.ps1 -Voice ru_RU-ruslan-medium
+pwsh -File install.ps1 -Voice en_US-amy-medium      # English female
+```
+
+Force re-download:
+
+```powershell
+pwsh -File install.ps1 -Force
+```
+
+## Use
+
+If `piper.exe` + a voice file are present in `tools/piper/`, J.A.R.V.I.S. auto-detects Piper on startup. No env vars required.
+
+To force a specific backend:
+
+```bat
+set JARVIS_TTS=piper      :: use Piper
+set JARVIS_TTS=sapi       :: force SAPI fallback
+set JARVIS_TTS=silero     :: use Silero (needs tools/silero/silero_tts.py)
+```
+
+Override paths:
+
+```bat
+set JARVIS_TTS_PIPER_BIN=D:\custom\piper.exe
+set JARVIS_TTS_PIPER_VOICE=D:\voices\my-voice.onnx
+```
+
+## Voices catalogue
+
+Full list: https://huggingface.co/rhasspy/piper-voices
+
+Recommended for Russian:
+- `ru_RU-irina-medium` — natural female, default
+- `ru_RU-dmitri-medium` — male, clear diction
+- `ru_RU-ruslan-medium` — male, slightly deeper
+- `ru_RU-denis-medium` — male, "newsreader" tone
+
+## Troubleshooting
+
+**"piper.exe not found"** — install script failed; check `install.ps1` output. The fallback is SAPI — assistant still works, just with the robotic voice.
+
+**"no .onnx voice in voices/"** — voice download failed (HuggingFace blocked?). Manually download from https://huggingface.co/rhasspy/piper-voices/tree/main/ru/ru_RU/irina/medium and drop both `.onnx` + `.onnx.json` into `voices/`.
+
+**Voice sounds wrong** — try a different model. Each Russian voice has a different timbre.
+
+**No audio output** — Piper writes to a temp wav, then plays via `System.Media.SoundPlayer` synchronously. Check that the default playback device isn't muted.