v0.2.1 — DS plugin-kit adoption (canonical boot)

Adopts plugin-kit.js for the handshake theming via dynamic import (it's an ESM — a classic <script src> throws on its exports; protoContent#224), replacing the hand-rolled theme map/listener. Normalized to the canonical boot block (one window.__base derivation shared by the CSS link + kit import). No data routes, so nothing to gate.

First tagged release. From the 2026-06-12 protoAgent plugin-ecosystem hardening pass.