chore: remove knip, husky and lint-staged

Drop the unused knip dead-code check and the husky+lint-staged pre-commit hook pipeline. All checks remain covered by the CI workflow (lint, typecheck, i18n, tests).

docs/operations/cms-error-center.md

@@ -44,7 +44,7 @@ stack is diagnostic evidence, not an automatic root-cause determination.
 ## Dependencies
 
 `pnpm install --frozen-lockfile`, `pnpm deps:audit`, `pnpm typecheck`, `pnpm test`,
-`pnpm knip`, `pnpm biome:lint`, and `pnpm build` are the verification sequence.
+`pnpm biome:lint`, and `pnpm build` are the verification sequence.
 `pnpm analyze --output` writes a Next.js bundle analysis (not an application build).
 
 TinyMCE 8.9 is pinned in pnpm. `pnpm assets:editor` copies its runtime files and