Add Discord-native hybrid front-end for Jarvis (bot + bridge)

Transform isair/jarvis into a Discord-controlled voice assistant running on
the Ubuntu VNC desktop, keeping the mature ~39k-line Python brain intact.

- bot/ (Node + bun, discord.js): /자비스 slash commands (ephemeral),
  voice channel join + voice receive/playback, pluggable VNC screen broadcast
  (selfbot live / noVNC / screenshot)
- bridge/ (Python, Flask): wraps jarvis STT + run_reply_engine + Piper TTS
  behind a thin localhost HTTP API
- .env.example, scripts/ (start_bridge/start_bot/dev), README rewrite,
  docs/language-comparison.md and docs/vnc-xfce-setup.md

Language decision: hybrid (Python brain + Node/bun Discord layer) because
Discord blocks bot video; native screen broadcast only works via a Node
selfbot library.

src/jarvis/tools/builtin/screenshot.py

@@ -0,0 +1,69 @@
+"""Screenshot tool implementation for OCR capture."""
+
+from typing import Dict, Any, Optional
+import os
+import tempfile
+import subprocess
+import shutil
+from ...debug import debug_log
+from ..base import Tool, ToolContext
+from ..types import ToolExecutionResult
+
+class ScreenshotTool(Tool):
+    """Tool for capturing screenshots and performing OCR."""
+
+    @property
+    def name(self) -> str:
+        return "screenshot"
+
+    @property
+    def description(self) -> str:
+        return "Capture a selected screen region and OCR the text. Use only if the OCR will materially help."
+
+    @property
+    def inputSchema(self) -> Dict[str, Any]:
+        return {
+            "type": "object",
+            "properties": {},
+            "required": []
+        }
+
+    def run(self, args: Optional[Dict[str, Any]], context: ToolContext) -> ToolExecutionResult:
+        """Execute the screenshot tool."""
+        context.user_print("📸 Capturing a screenshot for OCR…")
+        debug_log("screenshot: capturing OCR...", "screenshot")
+        # Inline OCR capture logic (previously in separate helper)
+        ocr_text: str = ""
+        sc = shutil.which("screencapture")
+        if sc:
+            tmpdir = tempfile.mkdtemp(prefix="jarvis_ocr_")
+            png_path = os.path.join(tmpdir, "shot.png")
+            try:
+                cmd = [sc, "-i", png_path]
+                try:
+                    ret = subprocess.run(cmd)
+                except Exception:
+                    ret = None  # type: ignore
+                if ret and getattr(ret, "returncode", 1) == 0 and os.path.exists(png_path):
+                    tess = shutil.which("tesseract")
+                    if tess:
+                        try:
+                            import pytesseract  # type: ignore
+                            from PIL import Image  # type: ignore
+                            with Image.open(png_path) as im:
+                                text = pytesseract.image_to_string(im)
+                                if text and text.strip():
+                                    ocr_text = text.strip()
+                        except Exception:
+                            pass
+            finally:
+                try:
+                    if os.path.exists(png_path):
+                        os.remove(png_path)
+                    os.rmdir(tmpdir)
+                except Exception:
+                    pass
+        debug_log(f"screenshot: ocr_chars={len(ocr_text)}", "screenshot")
+        context.user_print("✅ Screenshot processed.")
+        # Return raw OCR text as tool result (no LLM processing here)
+        return ToolExecutionResult(success=True, reply_text=ocr_text)