`sendVideo` gives back `width=320 height=320 duration=0` with no thumbnail once an
upload is large enough that Telegram skips its own video processing, and clients
then draw the message as a square tile — for portrait reels and 16:9 clips alike,
even though the delivered file itself is correct.
Measured on one 6 s 2560x1440 clip, inspecting the Bot API response: 4.9 MB and
9.8 MB keep `2560x1440` / duration 7 / a 320x180 thumbnail; 14.8 MB, 19.4 MB and
23.0 MB degrade to the square placeholder; the same 23.0 MB file sent with
`width`/`height`/`duration` plus a JPEG `thumbnail` comes back `2560x1440` with a
320x180 thumbnail.
Probe the local file with ffprobe and attach a 320px-wide JPEG frame from it, on
both Telegram send paths: the gateway adapter's `send_video` and the standalone
`hermes send` media sender. Both helpers return nothing when ffmpeg/ffprobe is
unavailable, which keeps the previous behaviour for hosts without them.
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