chore: initialize gentoo-setup documentation repository

Add comprehensive documentation for Lenovo ThinkPad Gentoo Linux setup
including:
- Complete system configuration guides (power, Bluetooth, WiFi, audio)
- Hardware setup documentation (touchpad, touchscreen, DisplayLink)
- Management scripts with ZSH completions
- Kernel configuration (6.12.41-gentoo-x86_64)
- Lid automation and monitor management
- Battery conservation system
- User guides and troubleshooting

Repository includes .gitignore to exclude logs, temporary files, and
secrets.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/battery-setup/battery-thresholds.conf

@@ -0,0 +1,22 @@
+# Configuration for battery-thresholds OpenRC service
+# Place this file in /etc/conf.d/battery-thresholds
+
+# Battery device (usually BAT0)
+BATTERY="BAT0"
+
+# Start charging when battery drops below this percentage
+START_THRESHOLD="20"
+
+# Stop charging when battery reaches this percentage
+END_THRESHOLD="80"
+
+# Conservation Mode (Recommended for docked/daily use):
+# START_THRESHOLD="20"
+# END_THRESHOLD="80"
+#
+# Full Charge Mode (For travel/extended unplugged use):
+# START_THRESHOLD="0"
+# END_THRESHOLD="100"
+#
+# Custom Mode:
+# Set any values between 0-100 where START < END