feat: type the plugin host record, move plugin strings out of core and add lint checks

src/backend/tests/fixtures/upgrade/upgrade-postgres.sql

@@ -462,6 +462,13 @@ CREATE UNIQUE INDEX "idx_host_protocol_auth_host_protocol" ON "host_protocol_aut
 CREATE INDEX "idx_host_protocol_auth_user" ON "host_protocol_auth" USING btree ("user_id");--> statement-breakpoint
 CREATE INDEX "idx_host_protocol_auth_credential" ON "host_protocol_auth" USING btree ("credential_id");
 
+-- ==== core 0064_sticky_pestilence ====
+-- ssh_data.autostart_password, autostart_key and autostart_key_password held
+-- copies of a host's login for 2.8's autostart endpoint, which nothing has read
+-- since. They leave the schema but stay in place, unused, until 3.0.0, so no
+-- install loses what it stored.
+SELECT 1;
+
 -- ==== plugin workspaces 0001_adopt_user_workspaces.sql ====
 -- workspaces 0001: adopt_user_workspaces
 -- Generated by termix-plugin migrations. Review before committing.