New test programs that exercise the cache-only Node server path and
compare its output against the legacy upstream-fetching path:
- test-cache-api-ready.js: pre-flight check that the cache file matches
what /api/releases would return for each name in _cache/<yyyy-mm>/.
- test-cache-compat.js: parameterized cache vs. fresh-fetch diff suite,
walks every package and OS/arch combo.
- test-api-compat.js, test-installer-resolve.js, test-broad-resolve.js:
installer-side parity checks across the resolver.
- test-live-compare.js, test-live-cache-diff.js,
test-live-installer-diff.js: TSV-output sweeps comparing two remote
URLs across the cached package x OS/arch matrix; supports
--concurrency and --packages filters.
- test-fleet-diff.js: fleet-wide TSV diff with package/OS/arch
filtering, used to validate beta and next.
Also adds 36 golden snapshots under _webi/testdata/live_*.json covering
6 packages (bat, caddy, go, jq, node, rg) x 4 OS/arch combos plus the
unfiltered baseline per package.
