fix: skip disposable pictures during local seek preroll

TODO.md

@@ -6,6 +6,7 @@
     - multi-file Open/Finder/drop, natural filename order, editable queue sidebar, explicit append, previous/next and automatic advance; Cast navigation retains the receiver; UI/drag-drop and physical-Cast verification remain unverified
 - [x] make sure the `make install` command installs the application (i can't find it in spotlight)
     - installs to ~/Applications, migrates the old hidden app, registers with Launch Services and requests Spotlight indexing; actual install, CLI, code signature, registration and Spotlight query passed; Spotlight UI remains unverified
-- [ ] takes an awfully long time seek in local videos which i find weird, since seeking in streamed youtube videos is pretty much instant
+- [x] takes an awfully long time seek in local videos which i find weird, since seeking in streamed youtube videos is pretty much instant
+    - local seek preroll skips disposable non-reference pictures without sacrificing exact target frames; measured 1080p/10-second-GOP paused seek improved from 541 ms to 400 ms and playing seek from 682 ms to 488 ms; timestamp/pixel checks passed across six decoder formats; long-GOP reference decoding remains necessary, and the originally affected files still need manual verification
 - [ ] in the "choose what to play" screen, we should change the youtube button to general streaming
 	- we can figure out the stream and how to handle it from the url (i.e. if youtube url, handle as youtube stream; if miruro url, handle accordingly)