Three strictness flags that the codebase already satisfies (0 errors each):
- noFallthroughCasesInSwitch on src + e2e — a missing `break` is now a type error.
- noUnusedLocals + noUnusedParameters on the e2e project, so it matches src and node
and dead spec scaffolding can't accumulate (it was the one project without them).
- allowJs + checkJs on the node project, pulling tailwind.config.js and
postcss.config.js under the type checker (the last hole in C-4.5) — a real type
error in either is now caught (verified: `content: 123` fails; Config stays
permissive on plugin keys by design).
noUncheckedIndexedAccess is NOT here — it has 98 call-site fixes and lands as its own
reviewable sub-sprint (S3b).
Locks the five flows the refactor must not break (feed, channel, player,
settings, nav) so later sprints can prove they changed nothing. Adds a thin
data-testid layer and a dedicated seeded non-demo account; the suite runs on
the baked :8080 stack (authoritative) or :5173. No product-behaviour change.
peter