vitest parses a bare `--update` as taking the next positional as its
value, so `make ui-visual-update UI_ARGS=<path>` handed the path to the
flag and ran with no filter at all: 99 files, every baseline in the repo
re-recorded, any stale one blessed in silence. Two paths were worse
still — the first was eaten and only the second ran.
That is #196's own hazard living in the tool meant to resolve it: the
rule is "refresh the reference your change moved and never one you did
not cause", and the documented way to refresh one refreshed the set.
`--update=true` is the whole fix, with the reason beside it because
`=true` reads like something to tidy away. `make ui-visual` and
`make ui-test` are unaffected — their `$(UI_ARGS)` follows `run`, with
no flag to swallow it — and no other target interpolates a variable
after a boolean flag.
Closes#204
logan