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, 80 insertions, 0 deletions

diff --git a/src/features/workspaces/store.svelte.ts b/src/features/workspaces/store.svelte.ts
new file mode 100644
index 0000000..0f662dc
--- /dev/null
+++ b/src/features/workspaces/store.svelte.ts
@@ -0,0 +1,80 @@
+import type { EnsureWorkspaceRequest } from "@dispatch/transport-contract";
+import type { Workspace, WorkspaceEntry } from "@dispatch/wire";
+import type { WorkspaceHttp, WorkspaceResult } from "./adapter/http";
+
+/**
+ * Workspace store — a thin reactive wrapper over the pure HTTP edge. Owns the
+ * list + loading/error state; mutations call the injected `WorkspaceHttp` and
+ * refresh the list. State is per-instance (no ambient store); subscriptions are
+ * owned by the composition root.
+ */
+export interface WorkspaceStore {
+	/** All workspaces (sorted by lastActivityAt desc by the backend). */
+	readonly list: readonly WorkspaceEntry[];
+	readonly loading: boolean;
+	readonly error: string | null;
+	/** Refresh the list from the backend. */
+	refresh(): Promise<void>;
+	/** `PUT /workspaces/:id` (create-on-miss). Returns the workspace or an error. */
+	ensure(id: string, body?: EnsureWorkspaceRequest): Promise<WorkspaceResult<Workspace>>;
+	/** Rename a workspace (display only; id unchanged). */
+	rename(id: string, title: string): Promise<WorkspaceResult<Workspace>>;
+	/** Set/clear a workspace's default cwd. */
+	setDefaultCwd(id: string, defaultCwd: string | null): Promise<WorkspaceResult<Workspace>>;
+	/** Delete a workspace (closes its conversations, reassigns to "default"). */
+	remove(id: string): Promise<WorkspaceResult<{ closedCount: number }>>;
+}
+
+export function createWorkspaceStore(http: WorkspaceHttp): WorkspaceStore {
+	let list = $state<readonly WorkspaceEntry[]>([]);
+	let loading = $state(false);
+	let error = $state<string | null>(null);
+
+	return {
+		get list(): readonly WorkspaceEntry[] {
+			return list;
+		},
+		get loading(): boolean {
+			return loading;
+		},
+		get error(): string | null {
+			return error;
+		},
+
+		async refresh(): Promise<void> {
+			loading = true;
+			error = null;
+			try {
+				list = await http.list();
+			} catch (err) {
+				error = err instanceof Error ? err.message : "Failed to load workspaces";
+			} finally {
+				loading = false;
+			}
+		},
+
+		async ensure(id, body): Promise<WorkspaceResult<Workspace>> {
+			const result = await http.ensure(id, body);
+			if (result.ok) void this.refresh();
+			return result;
+		},
+
+		async rename(id, title): Promise<WorkspaceResult<Workspace>> {
+			const result = await http.setTitle(id, title);
+			if (result.ok) void this.refresh();
+			return result;
+		},
+
+		async setDefaultCwd(id, defaultCwd): Promise<WorkspaceResult<Workspace>> {
+			const result = await http.setDefaultCwd(id, defaultCwd);
+			if (result.ok) void this.refresh();
+			return result;
+		},
+
+		async remove(id): Promise<WorkspaceResult<{ closedCount: number }>> {
+			const result = await http.delete(id);
+			if (result.ok) void this.refresh();
+			return result;
+		},
+	};
+}