feat(kiosk): resolve constant plugin IDs, overrides and the CheckT helper

- kiosk.ReadIdentity: ID()/Requires() as literals or constants across packages and modules, read with go/parser, never run
- plugin minimums from go.mod requires; v0.0.0 is an error, a pseudo-version warns
- kiosk.Validate, kiosk.CheckT (no testing import)
- plugin:add reads IDs through kiosk.ReadIdentity, so const-ID plugins register

modules/kiosk/testdata/literal/plugin.yaml

@@ -0,0 +1,8 @@
+# Generated by summer plugin:manifest. Do not edit; rerun the command.
+schema: 1
+id: acme.blog
+module: example.test/sm-acme-plugin
+package: example.test/sm-acme-plugin
+name: Blog
+description: Posts and categories for an acme application, with a feed.
+framework: v0.5.3