Trim fzf::select output before parsing
fzf appends a trailing newline to its stdout. The String FromStr impl
is just a clone, so picked-string callers (`pick_namespace`,
`PropAction::Set` value/key picker) saw "noah\n" and forwarded that
through to validate_namespace, which rightly rejected the embedded
newline.
Also affected non-string callers in principle (Id from "tsk-1\n"
parses the int part as "1\n", which fails) but no live caller hit
that yet.
Trim once in fzf::select so every caller benefits.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>