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/src/skywalker_tui/app.py

@@ -9,13 +9,6 @@ with Textual's built-in App.mode / _current_mode / _screen_stacks system.
 
 import argparse
 import sys
-import os
-from pathlib import Path
-
-# Add tools directory to path for skywalker_lib import
-_tools_dir = str(Path(__file__).resolve().parent.parent.parent.parent / "tools")
-if _tools_dir not in sys.path:
-    sys.path.insert(0, _tools_dir)
 
 from textual.app import App, ComposeResult
 from textual.binding import Binding
@@ -57,14 +50,17 @@ class SkyWalkerApp(App):
         Binding("f5", "rf_mode('track')", "Track", show=True),
         Binding("q", "quit", "Quit", show=True),
         Binding("d", "toggle_dark", "Theme", show=True),
+        Binding("ctrl+w", "starwars", "Star Wars", show=False),
     ]
 
-    def __init__(self, bridge: USBBridge, initial_mode: str = "spectrum"):
+    def __init__(self, bridge: USBBridge, initial_mode: str = "spectrum",
+                 show_splash: bool = True):
         super().__init__()
         self._bridge = bridge
         self._initial_rf_mode = initial_mode
         self._active_rf_mode = initial_mode
         self._rf_screens: dict[str, object] = {}
+        self._show_splash = show_splash
 
     def compose(self) -> ComposeResult:
         yield Header()
@@ -81,18 +77,35 @@ class SkyWalkerApp(App):
         yield Footer()
 
     def on_mount(self) -> None:
-        # Initialize status bar
+        # Initialize status bar (lightweight)
         status = self.query_one(DeviceStatusBar)
         status.update_status(self._bridge)
 
-        # Install all mode screens into the content switcher
+        if self._show_splash:
+            # Push splash FIRST, then init mode screens behind it.
+            # Two-tick chain: tick 1 = splash renders, tick 2 = heavy work.
+            self.call_later(self._push_splash)
+        else:
+            self.call_later(self._init_mode_screens)
+
+    def _push_splash(self) -> None:
+        """Push splash screen, then defer heavy mode screen init."""
+        from skywalker_tui.screens.splash import SplashScreen
+        try:
+            self.push_screen(SplashScreen())
+        except Exception:
+            pass
+        # Mode screens mount behind the splash overlay — pre-baked ANSI art
+        # renders instantly so no delay needed before heavy work starts
+        self.call_later(self._init_mode_screens)
+
+    def _init_mode_screens(self) -> None:
+        """Mount all 5 mode screens into the content switcher."""
         switcher = self.query_one("#content-area", ContentSwitcher)
         for mode_key, (_label, cls) in MODES.items():
             screen = cls(self._bridge, id=f"screen-{mode_key}")
             self._rf_screens[mode_key] = screen
             switcher.mount(screen)
-
-        # Activate initial mode
         self.action_rf_mode(self._initial_rf_mode)
 
     def action_rf_mode(self, mode: str) -> None:
@@ -110,7 +123,7 @@ class SkyWalkerApp(App):
             btn.remove_class("-active")
         self.query_one(f"#btn-{mode}", Button).add_class("-active")
 
-        self.sub_title = f"DVB-S RF Tool — {MODES[mode][0]}"
+        self.sub_title = f"DVB-S RF Tool \u2014 {MODES[mode][0]}"
 
     def on_button_pressed(self, event: Button.Pressed) -> None:
         """Handle sidebar mode button clicks."""
@@ -122,6 +135,25 @@ class SkyWalkerApp(App):
 
     def action_toggle_dark(self) -> None:
         self.dark = not self.dark
+        if self.dark:
+            self.notify(
+                "Welcome to the Dark Side.",
+                title="The Force is strong with this one",
+                severity="warning",
+                timeout=4,
+            )
+        else:
+            self.notify(
+                "The Force awakens.",
+                title="A New Hope",
+                severity="information",
+                timeout=4,
+            )
+
+    def action_starwars(self) -> None:
+        """Easter egg: stream ASCII Star Wars from telnet."""
+        from skywalker_tui.screens.starwars import StarWarsScreen
+        self.push_screen(StarWarsScreen())
 
 
 def main():
@@ -133,6 +165,10 @@ def main():
         "--demo", action="store_true",
         help="Use synthetic signal data (no hardware required)",
     )
+    parser.add_argument(
+        "--no-splash", action="store_true",
+        help="Skip the splash screen on startup",
+    )
     parser.add_argument(
         "mode", nargs="?", default="spectrum",
         choices=list(MODES.keys()),
@@ -158,7 +194,11 @@ def main():
             print("Use --demo for synthetic signal data.", file=sys.stderr)
             sys.exit(1)
 
-    app = SkyWalkerApp(bridge=bridge, initial_mode=args.mode)
+    app = SkyWalkerApp(
+        bridge=bridge,
+        initial_mode=args.mode,
+        show_splash=not args.no_splash,
+    )
     try:
         app.run()
     finally: