fix(worker): stop capping VapourSynth's frame cache at 1 GB (#107)

[StuartCameronCode]

Fixes #107.

Problem

Both templates set core.max_cache_size = 1024. The bundled VapourSynth R78 picks 8192 MB for itself on a 16 GB Mac, so the line cut the cache to an eighth. On HD sources that starves QTGMC's threads; the reporter saw ~1 fps and a log full of memory usage still over the limit, flushing pipeline.

Bare haf.QTGMC, synthetic interlaced 4:2:2, bundled vspipe (macos-arm64, 8 threads):

Source	Preset	Cache (MB)	fps
1920x1080	Slower	1024	6.5
1920x1080	Slower	default (8192)	18.0
1920x1080	Very Slow	1024	1.9
1920x1080	Very Slow	default (8192)	14.7
720x576	Slower	1024	92.8
720x576	Slower	default (8192)	89.5

SD never reaches the cap, which is why no test noticed.

Change

• Neither template sets the cache size on its own any more.
• Settings → Output → VapourSynth Cache → Override max cache size (EncodingSettings.maxCacheSizeMb, MB, off by default) writes core.max_cache_size into both the encode and preview scripts. 0 is treated as off.

Testing

• Rust test_162: both scripts, with and without the override.
• Flutter: script-generation test in integration_filter_parameters_test.dart, model tests in max_cache_size_test.dart.
• One real encode run locally with the cap removed.

Not measured: the default VapourSynth picks on Windows/Linux or on an 8 GB machine. The new control has not been checked by eye in the running app.

🤖 Generated with Claude Code

https://claude.ai/code/session_014GLXdGLfPwgYjW1AkonGqN