Add radar scope, splash screen, Star Wars easter egg, and harden TUI

New features:
- P1 green phosphor radar scope widget on Track screen with LUT-optimized rendering
- Splash screen with pre-baked ANSI half-block art from 16colo.rs/Mistigris
- Star Wars ASCII animation via telnet (ctrl+w) with IPv6 happy eyeballs and offline fallback
- Dark Side / New Hope toast notifications on theme toggle
- Kitty terminal detection with cat emoji on splash

Robustness (from Apollo code review):
- Circuit breaker in track loop after 10 consecutive errors
- Input validation for frequency, symbol rate, step size across scan/spectrum/track
- Consolidated sys.path manipulation into __init__.py
- Radar scope pre-computes dist/angle LUT per pixel on resize

Cleanup:
- Removed unused imports across lband, monitor, scan, signal_gauge
- Moved Pillow/textual-image to optional dev deps (splash uses pre-baked ANSI)
- Added 41-test pytest suite covering telnet IAC parsing, radar geometry, splash assets

tui/scripts/fetch_art.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+"""Download splash art from 16colo.rs for SkyWalker-1 TUI.
+
+Fetches pixel/teletext art from Mistigris packs on 16colo.rs and saves
+them as bundled assets for the splash screen.
+
+Usage:
+    python scripts/fetch_art.py
+"""
+
+import urllib.request
+import sys
+from pathlib import Path
+
+ASSETS_DIR = Path(__file__).resolve().parent.parent / "src" / "skywalker_tui" / "assets" / "splash"
+
+ART_SOURCES = [
+    {
+        "url": "https://16colo.rs/pack/mist0717/raw/ILLARTERATE-SETI-100_02_SATELLITE.PNG",
+        "filename": "seti-satellite.png",
+        "artist": "Illarterate",
+        "title": "S.E.T.I. Satellite",
+        "pack": "mist0717",
+    },
+    {
+        "url": "https://16colo.rs/pack/mist1119/raw/192.168.10.13-DIALTONE.JPG",
+        "filename": "dialtone.jpg",
+        "artist": "192.168.10.13",
+        "title": "Dialtone",
+        "pack": "mist1119",
+    },
+    {
+        "url": "https://16colo.rs/pack/mist0523/raw/BLIPPYPIXEL-SO_FAR_AWAY.GIF",
+        "filename": "so-far-away.gif",
+        "artist": "Blippypixel",
+        "title": "So Far Away",
+        "pack": "mist0523",
+    },
+    {
+        "url": "https://16colo.rs/pack/mist0121/raw/JELLICA_JAKE-PRODIGY.JPG",
+        "filename": "prodigy-out-of-space.jpg",
+        "artist": "Jellica Jake",
+        "title": "Prodigy / Out of Space",
+        "pack": "mist0121",
+    },
+    {
+        "url": "https://16colo.rs/pack/mist1120/raw/BLIPPYPIXEL-SPACE_DOCKER.GIF",
+        "filename": "space-docker.gif",
+        "artist": "Blippypixel",
+        "title": "Space Docker",
+        "pack": "mist1120",
+    },
+]
+
+
+def fetch_all():
+    ASSETS_DIR.mkdir(parents=True, exist_ok=True)
+    downloaded = 0
+
+    for art in ART_SOURCES:
+        dest = ASSETS_DIR / art["filename"]
+        if dest.exists():
+            print(f"  exists: {art['filename']}", file=sys.stderr)
+            downloaded += 1
+            continue
+
+        print(f"  fetch:  {art['filename']} from {art['url']}", file=sys.stderr)
+        try:
+            req = urllib.request.Request(art["url"], headers={"User-Agent": "SkyWalker-1-TUI/0.1"})
+            with urllib.request.urlopen(req, timeout=30) as resp:
+                data = resp.read()
+            dest.write_bytes(data)
+            print(f"          {len(data):,} bytes -> {dest.name}", file=sys.stderr)
+            downloaded += 1
+        except Exception as e:
+            print(f"  FAIL:   {art['filename']}: {e}", file=sys.stderr)
+
+    # Write CREDITS.md
+    credits = ASSETS_DIR / "CREDITS.md"
+    lines = ["# Splash Art Credits\n", ""]
+    lines.append("All artwork sourced from [16colo.rs](https://16colo.rs) /")
+    lines.append("[Mistigris](https://mistigris.com) art packs.\n")
+    lines.append("| File | Artist | Title | Pack |")
+    lines.append("|------|--------|-------|------|")
+    for art in ART_SOURCES:
+        pack_url = f"https://16colo.rs/pack/{art['pack']}"
+        lines.append(
+            f"| `{art['filename']}` | {art['artist']} "
+            f"| {art['title']} | [{art['pack']}]({pack_url}) |"
+        )
+    lines.append("")
+    credits.write_text("\n".join(lines))
+
+    print(f"\n  {downloaded}/{len(ART_SOURCES)} images downloaded to {ASSETS_DIR}", file=sys.stderr)
+    return downloaded
+
+
+if __name__ == "__main__":
+    fetch_all()