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/install.ps1

@@ -0,0 +1,108 @@
+#requires -Version 5.1
+<#
+.SYNOPSIS
+  Download Piper TTS engine + Russian voice into tools/piper/.
+
+.DESCRIPTION
+  Fetches the latest piper_windows_amd64.zip from rhasspy/piper-binary and
+  the Irina (ru_RU) voice .onnx + .json from huggingface rhasspy/piper-voices.
+  Idempotent — skips if files already exist. Pass -Force to re-download.
+
+.PARAMETER Voice
+  Voice name to install. Default "ru_RU-irina-medium". Other options:
+  ru_RU-denis-medium, ru_RU-dmitri-medium, ru_RU-ruslan-medium, en_US-amy-medium, ...
+
+.PARAMETER Force
+  Re-download even if files exist.
+
+.EXAMPLE
+  pwsh -File install.ps1
+  pwsh -File install.ps1 -Voice ru_RU-denis-medium
+  pwsh -File install.ps1 -Force
+#>
+
+param(
+    [string]$Voice = "ru_RU-irina-medium",
+    [switch]$Force
+)
+
+$ErrorActionPreference = "Stop"
+$InformationPreference = "Continue"
+
+$Root = Split-Path -Parent $MyInvocation.MyCommand.Path
+$BinPath = Join-Path $Root "piper.exe"
+$VoiceDir = Join-Path $Root "voices"
+$VoiceFile = Join-Path $VoiceDir "$Voice.onnx"
+$VoiceJson = Join-Path $VoiceDir "$Voice.onnx.json"
+
+# ─── Piper binary ──────────────────────────────────────────────────────────
+if ((Test-Path $BinPath) -and -not $Force) {
+    Write-Information "[skip] piper.exe already present at $BinPath"
+} else {
+    Write-Information "[fetch] piper_windows_amd64.zip..."
+    $zip = Join-Path $env:TEMP "piper_windows_amd64.zip"
+    $url = "https://github.com/rhasspy/piper/releases/latest/download/piper_windows_amd64.zip"
+    Invoke-WebRequest -Uri $url -OutFile $zip -UseBasicParsing
+    Write-Information "[unzip] -> $Root"
+    Expand-Archive -Path $zip -DestinationPath $Root -Force
+    # piper distributes inside a "piper/" subfolder — flatten it
+    $inner = Join-Path $Root "piper"
+    if (Test-Path $inner) {
+        Get-ChildItem -Path $inner -Force | Move-Item -Destination $Root -Force
+        Remove-Item -Path $inner -Recurse -Force
+    }
+    Remove-Item $zip -Force
+    if (-not (Test-Path $BinPath)) {
+        throw "piper.exe not found after extraction"
+    }
+    Write-Information "[ok] piper installed at $BinPath"
+}
+
+# ─── Voice files ───────────────────────────────────────────────────────────
+if (-not (Test-Path $VoiceDir)) {
+    New-Item -ItemType Directory -Path $VoiceDir | Out-Null
+}
+
+# Voice naming: ru_RU-irina-medium -> lang=ru_RU, name=irina, quality=medium
+$parts = $Voice -split "-"
+if ($parts.Length -lt 3) {
+    throw "Bad voice name '$Voice' — expected <lang>-<name>-<quality>"
+}
+$lang = $parts[0]
+$name = $parts[1]
+$quality = $parts[2]
+$langCode = ($lang -split "_")[0]
+
+$Base = "https://huggingface.co/rhasspy/piper-voices/resolve/main/$langCode/$lang/$name/$quality"
+
+foreach ($pair in @(
+    @{ url = "$Base/$Voice.onnx"; out = $VoiceFile },
+    @{ url = "$Base/$Voice.onnx.json"; out = $VoiceJson }
+)) {
+    if ((Test-Path $pair.out) -and -not $Force) {
+        Write-Information "[skip] $(Split-Path -Leaf $pair.out) already present"
+        continue
+    }
+    Write-Information "[fetch] $($pair.url)"
+    Invoke-WebRequest -Uri $pair.url -OutFile $pair.out -UseBasicParsing
+    Write-Information "[ok] $(Split-Path -Leaf $pair.out) -> $($pair.out)"
+}
+
+# ─── Smoke test ────────────────────────────────────────────────────────────
+$testWav = Join-Path $env:TEMP "jarvis-piper-test.wav"
+try {
+    Write-Information "[test] synthesizing 'Привет, Дмитрий'..."
+    "Привет, Дмитрий" | & $BinPath --model $VoiceFile --output_file $testWav 2>$null
+    if ((Test-Path $testWav) -and ((Get-Item $testWav).Length -gt 1000)) {
+        Write-Information "[ok] Piper works! Test wav: $testWav"
+        Write-Information ""
+        Write-Information "Next: set environment variable JARVIS_TTS=piper"
+        Write-Information "      (or just leave it unset — auto-detect will pick Piper)"
+    } else {
+        Write-Warning "Test wav empty or missing — synthesis may have failed"
+    }
+} catch {
+    Write-Warning "Smoke test failed: $_"
+} finally {
+    if (Test-Path $testWav) { Remove-Item $testWav -Force }
+}