feat: workspaces shell + cwd-lsp rename + mcp/settings/system-prompt features + app wiring

- workspaces: URL-driven conversation grouping (home listing at /, routing,
  store, http adapter, WorkspaceCard) wired into the App.svelte shell
- rename features/workspace -> features/cwd-lsp (the cwd/lsp status feature)
- new features: mcp (status view), settings (chat-limit field), system-prompt
  (prompt builder), all rendered via the generic surface host
- chat: store + ChatView updates
- tabs: tabs-store updates
- app wiring: ErrorModal (full-screen error surface), app/App.svelte + store.svelte

This commit makes HEAD typecheck clean for the first time: the prior HEAD
(dfe1711) imported features/settings from app/App.svelte but never committed
the feature, so only the full working tree was green.

1 files changed, 133 insertions, 0 deletions

diff --git a/src/features/workspaces/adapter/http.test.ts b/src/features/workspaces/adapter/http.test.ts
new file mode 100644
index 0000000..adaff00
--- /dev/null
+++ b/src/features/workspaces/adapter/http.test.ts
@@ -0,0 +1,133 @@
+import { describe, expect, it, vi } from "vitest";
+import { createWorkspaceHttp } from "./http";
+
+/** Build a fake `fetch` returning a canned Response. */
+function fakeFetch(responses: Array<{ status?: number; body?: unknown } | Error>): typeof fetch {
+	let i = 0;
+	return vi.fn(async () => {
+		const next = responses[i++];
+		if (next === undefined) throw new Error("fakeFetch: no more canned responses");
+		if (next instanceof Error) throw next;
+		const status = next.status ?? 200;
+		const body = next.body;
+		return {
+			ok: status >= 200 && status < 300,
+			status,
+			async json() {
+				return body;
+			},
+		} as Response;
+	}) as unknown as typeof fetch;
+}
+
+const BASE = "http://x";
+
+describe("createWorkspaceHttp", () => {
+	it("list returns the workspaces", async () => {
+		const fetchImpl = fakeFetch([
+			{
+				body: {
+					workspaces: [
+						{
+							id: "a",
+							title: "A",
+							defaultCwd: null,
+							createdAt: 1,
+							lastActivityAt: 2,
+							conversationCount: 3,
+						},
+					],
+				},
+			},
+		]);
+		const http = createWorkspaceHttp(BASE, fetchImpl);
+		const list = await http.list();
+		expect(list).toHaveLength(1);
+		expect(list[0]?.id).toBe("a");
+		expect(list[0]?.conversationCount).toBe(3);
+		expect(fetchImpl).toHaveBeenCalledWith(`${BASE}/workspaces`);
+	});
+
+	it("list returns [] on a failed response (non-fatal)", async () => {
+		const http = createWorkspaceHttp(BASE, fakeFetch([{ status: 500 }]));
+		expect(await http.list()).toEqual([]);
+	});
+
+	it("list returns [] on a network error", async () => {
+		const http = createWorkspaceHttp(BASE, fakeFetch([new Error("network")]));
+		expect(await http.list()).toEqual([]);
+	});
+
+	it("ensure PUTs the id + returns the workspace", async () => {
+		const ws = { id: "my-ws", title: "my-ws", defaultCwd: null, createdAt: 10, lastActivityAt: 10 };
+		const fetchImpl = fakeFetch([{ body: ws }]);
+		const http = createWorkspaceHttp(BASE, fetchImpl);
+		const result = await http.ensure("my-ws");
+		expect(result).toEqual({ ok: true, value: ws });
+		expect(fetchImpl).toHaveBeenCalledWith(
+			`${BASE}/workspaces/my-ws`,
+			expect.objectContaining({ method: "PUT" }),
+		);
+	});
+
+	it("ensure surfaces the backend error on a 400 (invalid slug)", async () => {
+		const http = createWorkspaceHttp(
+			BASE,
+			fakeFetch([{ status: 400, body: { error: "invalid slug" } }]),
+		);
+		const result = await http.ensure("UPPER");
+		expect(result).toEqual({ ok: false, error: "invalid slug" });
+	});
+
+	it("get returns null on 404", async () => {
+		const http = createWorkspaceHttp(BASE, fakeFetch([{ status: 404 }]));
+		expect(await http.get("nope")).toBeNull();
+	});
+
+	it("get returns the workspace on 200", async () => {
+		const ws = { id: "x", title: "X", defaultCwd: "/home", createdAt: 1, lastActivityAt: 2 };
+		const http = createWorkspaceHttp(BASE, fakeFetch([{ body: ws }]));
+		expect(await http.get("x")).toEqual(ws);
+	});
+
+	it("setTitle PUTs the title", async () => {
+		const ws = { id: "a", title: "Renamed", defaultCwd: null, createdAt: 1, lastActivityAt: 2 };
+		const fetchImpl = fakeFetch([{ body: ws }]);
+		const http = createWorkspaceHttp(BASE, fetchImpl);
+		const result = await http.setTitle("a", "Renamed");
+		expect(result).toEqual({ ok: true, value: ws });
+		const call = (fetchImpl as unknown as ReturnType<typeof vi.fn>).mock.calls[0];
+		expect(call?.[0]).toBe(`${BASE}/workspaces/a/title`);
+		expect(JSON.parse(call?.[1]?.body)).toEqual({ title: "Renamed" });
+	});
+
+	it("setDefaultCwd PUTs null to clear", async () => {
+		const ws = { id: "a", title: "A", defaultCwd: null, createdAt: 1, lastActivityAt: 2 };
+		const fetchImpl = fakeFetch([{ body: ws }]);
+		const http = createWorkspaceHttp(BASE, fetchImpl);
+		await http.setDefaultCwd("a", null);
+		const call = (fetchImpl as unknown as ReturnType<typeof vi.fn>).mock.calls[0];
+		expect(call?.[0]).toBe(`${BASE}/workspaces/a/default-cwd`);
+		expect(JSON.parse(call?.[1]?.body)).toEqual({ defaultCwd: null });
+	});
+
+	it("delete returns closedCount", async () => {
+		const fetchImpl = fakeFetch([{ body: { workspaceId: "a", closedCount: 4 } }]);
+		const http = createWorkspaceHttp(BASE, fetchImpl);
+		const result = await http.delete("a");
+		expect(result).toEqual({ ok: true, value: { closedCount: 4 } });
+		expect(fetchImpl).toHaveBeenCalledWith(
+			`${BASE}/workspaces/a`,
+			expect.objectContaining({ method: "DELETE" }),
+		);
+	});
+
+	it("delete surfaces 409 for 'default'", async () => {
+		const http = createWorkspaceHttp(
+			BASE,
+			fakeFetch([{ status: 409, body: { error: "cannot delete default" } }]),
+		);
+		const result = await http.delete("default");
+		expect(result).toEqual({ ok: false, error: "cannot delete default" });
+	});
+});