Plugin Docs

These docs are split from plugins/PLUGINS.md so each plugin area has a smaller reference.

File	Covers
bundle-format.md	Bundle layout, manifest fields, nav entries, TypeScript entrypoints.
server-side-plugins.md	Server-only plugin runtime, RPC/SSE, persistent data, build hooks, build UI settings/actions.
install-and-manage.md	Uploading, opening, enabling, auto-load, Plugin Manager behavior.
samples.md	Included sample plugins and what each demonstrates.
legacy-native-plugins.md	Native plugins, direct OS/API use, native ABI, build scripts, static Linux shim.
signing.md	Ed25519 plugin signing and trusted key management.