fix(connections): preserve provider workspaces and follow-up context

Keep selected model and skill paths current across disposable connection homes. Preserve private Grok history and assigned OpenCode and Hermes workspaces. Fix artifact helper paths and cover the boundaries with regression checks.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

scripts/mcp-fixtures/servers/acp-filesystem-agent.mjs

@@ -0,0 +1,43 @@
+#!/usr/bin/env node
+// Credential-free ACP filesystem requests, driven through the real client.
+import { createInterface } from "node:readline";
+
+const pending = new Map();
+let nextId = 100;
+const send = (message) => process.stdout.write(`${JSON.stringify(message)}\n`);
+const request = (method, params) => new Promise((resolve) => {
+  const id = nextId++;
+  pending.set(id, resolve);
+  send({ jsonrpc: "2.0", id, method, params });
+});
+
+createInterface({ input: process.stdin }).on("line", async (line) => {
+  const message = JSON.parse(line);
+  if (pending.has(message.id)) {
+    pending.get(message.id)(message);
+    pending.delete(message.id);
+    return;
+  }
+  let result;
+  if (message.method === "initialize") {
+    result = {
+      protocolVersion: 1,
+      agentCapabilities: { loadSession: false, sessionCapabilities: { close: {} } },
+      agentInfo: { name: "paperclip-acp-filesystem-fixture", version: "1.0.0" },
+    };
+  } else if (message.method === "session/new") {
+    result = { sessionId: "filesystem-fixture" };
+  } else if (message.method === "session/prompt") {
+    const { operations } = JSON.parse(message.params.prompt.find((entry) => entry.type === "text").text);
+    for (const { method, ...params } of operations) {
+      const response = await request(method, { sessionId: "filesystem-fixture", ...params });
+      process.stderr.write(`FS_RESULT ${JSON.stringify(response)}\n`);
+    }
+    result = { stopReason: "end_turn" };
+  } else if (message.method === "session/cancel") {
+    return;
+  } else {
+    result = {};
+  }
+  if (message.id !== undefined) send({ jsonrpc: "2.0", id: message.id, result });
+});