macos-13 runner tier is being phased out by GitHub — queues persistently
exceeded 1 h during v0.9.0-rc1 build. Intel Mac users fall back to
'cargo install --features bundled-assets' from source, Docker
--platform linux/amd64, or a Linux VM.
Documents OXICLOUD_ENABLE_VIDEO_THUMBNAILS (+ OXICLOUD_FFMPEG_PATH) in
example.env and docs/config/env.md — closes the discoverability gap
where the env var was only visible in Rust docstrings.
Also lands docs/plan/bundled-binary.md — the design record referenced
from code comments in src/cli/mod.rs, src/interfaces/web/embedded.rs,
and the Dockerfile.
Edouard Vanbelle