build(frontend): knip also checks what ships; strict indexing in every project

`npm run knip` now runs a second, --production pass, which asks whether the
code that ships uses an export, not just whether anything does. Of the 47
exports only tests reached:
- 34 are exported for their test and say so with @internal, naming the test.
- 11 were module-private names with a stray `export`. Two of them were not
  used at all and are deleted.
- The unused alreadyReported re-export is gone.
Test kits, the e2e suite and the two build-tooling modules are excluded from
the production project, each named in knip.jsonc.

noUncheckedIndexedAccess is now on for the node and e2e tsconfigs too (0
errors), matching the app project. tsconfig.node.json listed a
tailwind.config.js that has not existed since Tailwind 4. That entry is now
playwright.config.ts, which the typed lint finds through this project.

frontend/src/components/ui/progressiveRows.ts

@@ -12,8 +12,9 @@ import { startTransition, useEffect, useState } from "react";
 //
 // Not virtualization: every row still ends up in the DOM, so browser find, keyboard nav past the screen,
 // and the Back focus/scroll restore (which wait for the list to grow) keep working as they did.
+/** @internal exported for DataTable.progressive.dom.test.tsx */
 export const FIRST_ROWS = 30;
-export const STEP_ROWS = 40;
+const STEP_ROWS = 40;
 
 // `view` names what the rows show (page, size, sort, filters). A new view starts over from the first
 // rows, so the urgent render after a click or a key stays small. New data for the same view (a refetch)