feat(plugin-sdk): one-command publish (pack → release → preflight → PR)

Collapses the release into a single command: pack the artifact, tag + create the
GitHub release, run the registry CI checks locally (preflight), and open the
registry PR — stopping before it submits if preflight would fail, so a broken
entry never becomes a doomed PR. `--sign` signs it; `--no-preflight` skips the
gate. The individual pack/release/preflight/submit commands still exist.

README + the Development/Publishing/Permissions wikis lead with `publish` now.

plugin-sdk/package.json

@@ -1,6 +1,6 @@
 {
   "name": "trek-plugin-sdk",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "SDK for building TREK plugins: types, definePlugin, a mock host, manifest validation, and the create-trek-plugin / trek-plugin CLIs.",
   "type": "module",
   "license": "MIT",