set red power cap via power-limit instead of amd-smi

[teddytennant]

amd-smi set --power-cap took one argument through ROCm 7.1 and takes two from 7.2. In amdsmi_cli/amdsmi_parser.py it went from action='store', metavar='WATTS' (7.1.0:1283) to nargs=2, metavar=('PWR_TYPE','WATTS') (7.2.0:1362), which is where expected 2 arguments comes from. 6.4.0 and 7.0.0 both carry the old shape, so the break lands exactly at 7.2, and 02install-drivers.sh now installs SDK 7.14, which has the new one.

Rather than track the amd-smi CLI, this points the unit at tools/power-limit, which already sets the red cap by writing power1_cap directly and validates against power1_cap_min/power1_cap_max. 11symlink.sh:10 symlinks it to /usr/local/bin/power-limit inside the same [[ -z "$TINYBOX_CORE" ]] branch that installs this unit, and 00release.sh writes /etc/tinybox-release in pre.d before post.d runs, so both exist by the time the unit fires.

One behaviour change worth flagging: power-limit rejects an out-of-range value and exits 1, where amd-smi set -o 304 did not validate. On a card whose power1_cap_max is under 304 that turns a silent no-op into a failed oneshot.

I don't have a red box, so this is verified by reading the build scripts, not by booting an image.

Closes #5.