Bump FilmCraft to 4e2d0bc2 (part of #804)

[vangel76]

Part of #804.

Why

#819 (hardware video decoding) needs a newer FilmCraft than the pinned 2c5ba7a. The pin bump is the only part of that PR that touches existing code, so it is split out here to be reviewed on its own. #819 builds on this PR. This PR adds no filmcraft-platform dependency, no hardware setting and no register() call.

What changed

All filmcraft-* git deps move from 2c5ba7a (2026-10-03) to FilmCraft main 4e2d0bc2 (2026-10-10).

• API: MediaInfo.audio became audio_streams (audio() / has_audio()), and VideoStreamInfo gained hdr. Mechanical fixes in interchange, media and two tests.
• Behaviour 1, frame requests: FilmCraft now rounds a frame request to the track's nearest timestamp unit, halves up. The media pool asked for the middle of frame i; when the timescale equals the frame rate (our own 10 fps MP4 / MOV exports) that rounds onto frame i+1. The pool now asks a quarter of the way into the frame, which still tolerates timestamps rounded either way (one line in pool.rs). This fixed the export round-trips for H.264 / HEVC / AV1 / ProRes and the automation qa::kinetic test.
• Behaviour 2, VP9 tests: filmcraft_vp9::Decoder::new() now uses frame threads, so a picture can come out of a later call. The VP9 encoder tests expect one picture per call, so they use Decoder::with_threads(1). Only test code uses the VP9 decoder.
• Rotation and AAC downmix: adapted to the new FilmCraft behaviour (media/src/probe.rs, downmix.rs, pool.rs).
• Lockfile: new FilmCraft crates pulled in by filmcraft-export (render, text, captions, audio-dsp). No filmcraft-platform.

What maintainers must decide

Only the pin: whether to move to FilmCraft 4e2d0bc2.

Gates

cargo fmt --check, cargo clippy --workspace --all-targets -- -D warnings, full cargo test of effectcraft-media, -export, -interchange, -render, -engine, -host and -vp9enc (all green), cargo xtask layers, cargo xtask wasm. Assets unchanged.

🤖 Generated with Claude Code

[vangel76]

Merged current main and resolved conflicts in Cargo.toml (kept the new filmcraft rev for interchange/project/geom, and kept main's symphonia aiff entry).