Drop the Deno target

The deno step mapped every package to https://deno.land/x/pezkuwi/..., which
never existed (nor does @pezkuwi on JSR): it was red on every run, hidden by
continue-on-error. Decided 2026-10-07: no Deno build. The src/mod.ts entry
points (imported by nothing else, and the switch that makes the build emit
build-deno/), the import maps, the deno script and the CI step are removed.
The npm packages are unchanged; Deno users can import them as npm:.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

packages/util-crypto/src/mod.ts

@@ -1,4 +0,0 @@
-// Copyright 2017-2026 @pezkuwi/util-crypto authors & contributors
-// SPDX-License-Identifier: Apache-2.0
-
-export * from './index.js';