docs: list every npm alias for the qa gates

CONTRIBUTING.md said "Only a couple (`qa:map-source-tray`, `qa:transit`) have
an `npm run` alias". package.json defines five: `qa:map-source-tray`,
`qa:panel-resize`, `qa:street-level`, `qa:street-level:fixtures` and
`qa:transit`.

The two missing names are not incidental -- .github/workflows/ci.yml already
invokes `npm run qa:street-level:fixtures` and `npm run qa:panel-resize`, so a
contributor reading the guide is told to reach for `node scripts/<gate>.mjs`
for gates the project itself runs through npm.

Verified against package.json scripts and .github/workflows/ci.yml on main
(1df2a27).

CONTRIBUTING.md

@@ -54,8 +54,9 @@ head -40 scripts/qa-radio.mjs  # what this runnable gate proves and how to run i
 Runnable gate entrypoints document what they assert and how to invoke them.
 Most need a dev server; some also need a specific provider key or port. Follow
 the entrypoint's header rather than assuming every matching file accepts the
-same arguments. Only a couple (`qa:map-source-tray`, `qa:transit`) have an
-`npm run` alias.
+same arguments. Five have an `npm run` alias: `qa:map-source-tray`,
+`qa:panel-resize`, `qa:street-level`, `qa:street-level:fixtures` and
+`qa:transit`.
 
 If you aren't sure which gate covers your change, search `docs/CURRENT-STATE.md`
 for the feature: it names the gate for many of them, and it's the authoritative