release(0.2.1): bump to 0.2.1, skipping Windows ARM64 this cycle

The 0.2.0 release left wickra@npm stuck at 0.1.4 and never created a
GitHub Release entry because the brand-new `wickra-win32-arm64-msvc`
sub-package name was caught by npm's spam-detection filter on its first
publish attempt (same situation that affected `wickra-win32-x64-msvc`
through 0.1.4 until npm Support unblocked it). A support ticket is open;
until it is resolved, ship 0.2.1 for the five platforms whose
sub-packages are already on npm and re-add Windows ARM64 in a follow-up
release.

Changes for this cycle:
- bindings/node/package.json: remove "wickra-win32-arm64-msvc" from
  optionalDependencies and "aarch64-pc-windows-msvc" from
  napi.triples.additional.
- bindings/node/npm/win32-arm64-msvc/: removed (will be restored fresh
  once the npm name is unblocked).
- .github/workflows/release.yml: comment out the
  aarch64-pc-windows-msvc entry of the node-build matrix with a
  TODO/restore note.
- Bump every workspace and binding version to 0.2.1 (Cargo.toml,
  pyproject.toml, bindings/node/package.json, five npm/<target>
  templates, the wiki version table). Cargo.lock regenerated.
- CHANGELOG: new [0.2.1] block consolidating every fix that has landed
  on main since 0.2.0 (HV epsilon, examples CI step, fuzz cargo-fuzz
  install, MSRV 1.85 -> 1.86 / 1.77 -> 1.88, criterion 0.5 -> 0.8,
  tokio-tungstenite 0.24 -> 0.29, tick_aggregator gap-fill cap, every
  GitHub Action SHA-pin bump). Compare-link added.

The arm64 loader branch in bindings/node/index.js is left untouched: a
Windows ARM64 user installing 0.2.1 will get the standard
`Cannot find module 'wickra-win32-arm64-msvc'` error from the loader,
which is accurate. PyPI's win-arm64 wheel is unaffected.

Verified locally:
  cargo fmt/clippy/test --workspace --all-features -> 630 passed / 0 failed
  cargo build -p wickra-examples --bins -> clean
  cargo build -p wickra-node -> clean

.github/workflows/release.yml

@@ -168,7 +168,15 @@ jobs:
           - { host: macos-latest, target: x86_64-apple-darwin }
           - { host: macos-latest, target: aarch64-apple-darwin }
           - { host: windows-latest, target: x86_64-pc-windows-msvc }
-          - { host: windows-11-arm, target: aarch64-pc-windows-msvc }
+          # NOTE: aarch64-pc-windows-msvc is temporarily skipped for 0.2.1.
+          # The wickra-win32-arm64-msvc npm subpackage name is blocked by the
+          # npm spam-detection filter for new accounts (same situation that
+          # affected wickra-win32-x64-msvc through 0.1.4 until npm Support
+          # unblocked it). A support ticket is open; once the new arm64 name
+          # is unblocked this matrix entry will be restored alongside the
+          # corresponding optionalDependencies / napi.triples / npm/<target>
+          # entries in a follow-up release.
+          # - { host: windows-11-arm, target: aarch64-pc-windows-msvc }
     runs-on: ${{ matrix.host }}
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2