build(frontend)!: knip drops --production; plain knip stays

The production pass (7ed2ac4e, E32) asked "is this export used by what
ships?". No real hit: its only findings were 37 exports a test imports,
answered with 36 `@internal` JSDoc tags (E34 S2) — test-only exports, not
defects. Since then it has only ever asked for another tag. The tags go
with it (36, no longer read by anything), and so do the production-only
`!…!` exclusions in knip.jsonc and their register rows. Plain knip (unused
files, exports and dependencies) keeps running in the gate.

frontend/src/components/plexDetailAside.tsx

@@ -184,7 +184,6 @@ export function DetailKeywords({
 // The crew shows its first CREW_SHOWN names and a "Show N more" that opens the rest: the column beside the
 // text is the hero's tallest part, and twelve names ran it ~170px past the text (E31, the owner's call).
 // A list only a little longer than that shows whole: a toggle that hides one or two names saves no room.
-/** @internal exported for PlexInfo.dom.test.tsx */
 export const CREW_SHOWN = 6;
 const CREW_FOLD_OVER = CREW_SHOWN + 2;