build(gate)!: coverage leaves the gate and runs on demand

Both lanes printed a coverage total with no threshold (owner decision E32
D4). No real hit as a lane: the one time the number found anything (5 bugs,
E32) it was read by hand, and since then it was a line nobody acted on. It
was also the most expensive part of the vitest lane, and the run that
flaked in E35 S1. The vitest lane runs without --coverage, the pytest lane
runs plain pytest; docs/development.md gives both on-demand commands, and
the register row says why.

scripts/check.sh

@@ -120,8 +120,7 @@ pip_audit() {
 }
 
 if [ "$mode" = all ]; then
-  # --coverage prints the summary: read, never a threshold (E32 D4)
-  lane "vitest (+ coverage report)" frontend npm run --silent test -- --coverage
+  lane "vitest" frontend npm run --silent test
   # the production bundle, and devOnlyGuard, which fails it when dev-only code reaches it
   lane "vite build" frontend npx vite build --logLevel warn
   lane "pytest (pure-logic + DB lane)" pytest_lane