feat: add plugin worker protocol, bootstrap and plugin_storage table

Worker-side ctx proxy plus the message envelope it talks over, and the
per-plugin key/value table behind ctx.storage with migrations for all
three dialects. Rows cascade with the plugin so uninstalling leaves
nothing behind.

drizzle/postgres/0025_purple_squirrel_girl.sql

@@ -0,0 +1,10 @@
+CREATE TABLE "plugin_storage" (
+	"id" serial PRIMARY KEY NOT NULL,
+	"plugin_id" varchar(255) NOT NULL,
+	"key" varchar(255) NOT NULL,
+	"value" text NOT NULL,
+	"updated_at" varchar(255) DEFAULT CURRENT_TIMESTAMP NOT NULL
+);
+--> statement-breakpoint
+ALTER TABLE "plugin_storage" ADD CONSTRAINT "plugin_storage_plugin_id_plugins_id_fk" FOREIGN KEY ("plugin_id") REFERENCES "public"."plugins"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
+CREATE UNIQUE INDEX "idx_plugin_storage_plugin_key" ON "plugin_storage" USING btree ("plugin_id","key");

drizzle/postgres/meta/_journal.json

@@ -176,6 +176,13 @@
       "when": 1789751455415,
       "tag": "0024_flimsy_forge",
       "breakpoints": true
+    },
+    {
+      "idx": 25,
+      "version": "7",
+      "when": 1789991403847,
+      "tag": "0025_purple_squirrel_girl",
+      "breakpoints": true
     }
   ]
 }