Add FPS counter, VSync toggle, shader metadata system, and multi-pass infrastructure

- FPS counter in window title (updates every 500ms)
- F4 key toggles VSync on/off
- Shader metadata: Name and Author from comments
- iChannel metadata parsing for multi-pass support
- Base structures: ShaderBuffer, ShaderPass
- FBO/texture management functions
- Updated all 11 shaders with Name/Author metadata

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

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

data/music/_readme_and_license.txt

@@ -0,0 +1,41 @@
+Pack downloaded from Freesound
+----------------------------------------
+
+"Ambient pads"
+
+This Pack of sounds contains sounds by the following user:
+ - Mat397 ( https://freesound.org/people/Mat397/ )
+
+You can find this pack online at: https://freesound.org/people/Mat397/packs/27416/
+
+
+Licenses in this Pack (see below for individual sound licenses)
+---------------------------------------------------------------
+
+Creative Commons 0: http://creativecommons.org/publicdomain/zero/1.0/
+Attribution 3.0: http://creativecommons.org/licenses/by/3.0/
+
+
+Sounds in this Pack
+-------------------
+
+  * 618042__mat397__bad-electric-dark-pad.wav.wav
+    * url: https://freesound.org/s/618042/
+    * license: Creative Commons 0
+  * 618041__mat397__mangle-dark-pad.wav.wav
+    * url: https://freesound.org/s/618041/
+    * license: Creative Commons 0
+  * 486083__mat397__world-of-ants-pad.wav.wav
+    * url: https://freesound.org/s/486083/
+    * license: Attribution 3.0
+  * 485079__mat397__melancholic-flutes-pad.wav.wav
+    * url: https://freesound.org/s/485079/
+    * license: Attribution 3.0
+  * 485078__mat397__polyflute-pad.wav.wav
+    * url: https://freesound.org/s/485078/
+    * license: Attribution 3.0
+  * 485077__mat397__confused-voices.wav.wav
+    * url: https://freesound.org/s/485077/
+    * license: Attribution 3.0
+
+