Unfinished, continued in the next session: t() resolves key.one/.few/...
by the language's own plural rule, the parity check knows which forms a
language needs, 16 singular/plural key pairs are merged in every locale
and every count === 1 branch in the client uses the plural form. Still
open: the forms each locale needs for the remaining count strings, the
two new labels in every locale, and 35 tests that expect the old English
wording.
214 items came out of writing the tests. Real defects are corrected, dead code
is removed rather than covered, and the tests that pinned the old behaviour
move with them.
Also drops two agent coverage scratch files that slipped into the coverage PR
and adds the ignore rule that keeps them out.