Make local plugins manageable and debuggable (#3446)

* feat(plugins): expose Paseo API to local plugins

Plugin surfaces borrow the selected host connection while subprocess handlers receive an exclusively owned IPC session, so plugins can use normal workspace and agent operations without inventing another transport.

* feat(plugins): reload global enablement safely

Treat the global plugin switch as a live daemon setting and teach plugin automation to inspect it before acting. Enabling remains permission-gated because plugin backend code can access the daemon machine and client contributions execute inside the app.

* feat(plugins): expose plugin logs

Capture plugin stdout and stderr separately from IPC so authors can debug initialization, RPC, cleanup, and crash behavior from the app or CLI. Keep a bounded tail across lifecycle recovery while preserving structured output in the daemon log.

* fix(build): order plugin dependency builds

* test(plugins): align startup and CLI expectations

packages/server/src/terminal/terminal-session-controller.test.ts

@@ -12,6 +12,7 @@ import type { ServerMessage, TerminalSession, TerminalStateSnapshot } from "./te
 import { TerminalSessionController } from "./terminal-session-controller.js";
 import type { TerminalManager, TerminalsChangedEvent } from "./terminal-manager.js";
 import { isSameOrDescendantPath } from "../server/path-utils.js";
+import { PluginSessionSocket } from "../server/plugins/session-socket.js";
 
 function deferred<T>(): {
   promise: Promise<T>;
@@ -755,6 +756,21 @@ describe("terminal-session-controller backpressure snapshot fallback", () => {
     expect(frames.some((frame) => frame.opcode === TerminalStreamOpcode.Output)).toBe(true);
   });
 
+  test("uses plugin IPC queued bytes to enter the snapshot backpressure path", async () => {
+    const socket = new PluginSessionSocket({
+      send() {
+        return true;
+      },
+    });
+    socket.send(new Uint8Array(8 * 1024 * 1024));
+    const { pushOutput, frames } = await setup(() => socket.bufferedAmount);
+
+    pushOutput("p".repeat(300 * 1024));
+    await waitForCoalescerFlush();
+
+    expect(frames.some((frame) => frame.opcode === TerminalStreamOpcode.Snapshot)).toBe(true);
+  });
+
   test("falls back to a snapshot at the byte threshold when no backpressure signal exists", async () => {
     // A null reading means the transport (e.g. the multiplexed relay socket) gives
     // no signal; we can't distinguish a slow client from a fast one, so we keep the