feat(client): add the dsh-client-test-runtime package

A jsdom slot test runtime for feature specs: a real Cordis Context, the
production SlotsService and web-react renderer, and typed session/workspace
doubles (TestSessions implements ISessions with FixtureSession sessions;
TestWorkspaces implements IWorkspaces), so the compiler flags fixture drift
when a production face changes. Fixtures feed plain data: list rows,
conversation snapshots, and ISession-typed behavior stubs; provide-bundle
materialization runs the shared SessionProvideChannel.

DOM snapshot support: declare()/renderSlot() mount a single slot inside a
data-slot wrapper for local .snap capture, and a snapshot serializer folds
CSS-module class hashes to their semantic locals and collapses svg internals
to a content fingerprint. The typed provide() constrains declared-service
fakes to Partial of the service's outward face.

packages/client/test-runtime/src/workspaces.ts

@@ -0,0 +1,147 @@
+/** Test-owned workspaces face: the renderer standard-kit observable plus recorded actions. */
+import { createSnapshotStore } from '@deepseek-ai/dsh-client-runtime/client'
+import type {
+  IWorkspaces, SessionId, SnapshotStore, WorkspaceId, WorkspaceListState, WorkspaceView,
+} from '@deepseek-ai/dsh-client-runtime/client'
+import { workspaceListState } from './fixtures.ts'
+import type { Stabilizer } from './fixtures.ts'
+
+/**
+ * Workspaces test double. Implements the same IWorkspaces face features
+ * receive as `ctx.workspaces`, so a production face change breaks this
+ * double at compile time. Every action records into {@link
+ * TestWorkspaces.calls}; defaults are inert echoes — feature tests needing
+ * richer behavior replace them via {@link TestWorkspaces.stub}.
+ */
+export class TestWorkspaces implements IWorkspaces {
+  /** The useWorkspaces standard feed. */
+  readonly list: SnapshotStore<WorkspaceListState>
+
+  /** Calls observed on the action face, newest last. */
+  readonly calls: { method: string; args: unknown[] }[] = []
+
+  /** Replaceable action seat: feature tests may stub richer behavior. */
+  private readonly stubs = new Map<string, (...args: unknown[]) => unknown>()
+
+  /**
+   * @param stabilize - the owning runtime's act wrapper.
+   */
+  constructor(private readonly stabilize: Stabilizer) {
+    this.list = createSnapshotStore<WorkspaceListState>(workspaceListState())
+  }
+
+  /**
+   * Update the workspace list state through an immer draft.
+   * @param mutate - draft mutator.
+   */
+  async update(mutate: (draft: WorkspaceListState) => void): Promise<void> {
+    await this.stabilize(() => { this.list.update(mutate) })
+  }
+
+  /**
+   * Replace an action's behavior (the recorded call is still appended first).
+   * @param method - action name (e.g. 'connectWorkspace').
+   * @param impl - replacement behavior.
+   */
+  stub(method: string, impl: (...args: unknown[]) => unknown): void {
+    this.stubs.set(method, impl)
+  }
+
+  /**
+   * Connect a workspace to its reusable/new blank session (recorded). The
+   * default resolves the workspace id back as the session id; stub for
+   * cross-session flows.
+   * @param workspaceId - target workspace.
+   * @returns the connected session id.
+   */
+  async connectWorkspace(workspaceId: WorkspaceId): Promise<SessionId> {
+    this.calls.push({ method: 'connectWorkspace', args: [workspaceId] })
+    const stub = this.stubs.get('connectWorkspace')
+    if (stub !== undefined) return await (stub(workspaceId) as Promise<SessionId>)
+    return `session-of-${workspaceId}` as SessionId
+  }
+
+  /**
+   * New-session flow (recorded; stubbed behavior runs when installed).
+   * @param workspaceId - optional explicit workspace target.
+   */
+  startSession(workspaceId?: WorkspaceId): void {
+    this.calls.push({ method: 'startSession', args: [workspaceId] })
+    this.stubs.get('startSession')?.(workspaceId)
+  }
+
+  /**
+   * Create a Workspace (recorded). The default echoes a view derived from
+   * the input; stub for failure or list-coupled flows.
+   * @param input - exactly one Host create spelling.
+   * @returns the created Workspace view.
+   */
+  async create(input: { name: string } | { path: string }): Promise<WorkspaceView> {
+    this.calls.push({ method: 'create', args: [input] })
+    const stub = this.stubs.get('create')
+    if (stub !== undefined) return await (stub(input) as Promise<WorkspaceView>)
+    const title = 'name' in input ? input.name : input.path
+    return {
+      workspaceId: `ws-${title}` as WorkspaceId,
+      title,
+      path: 'path' in input ? input.path : `/${input.name}`,
+      sessionIds: [],
+    } as unknown as WorkspaceView
+  }
+
+  /**
+   * Open a path with the host OS default application (recorded; default no-op).
+   * @param path - host-resolvable path.
+   */
+  async openPath(path: string): Promise<void> {
+    this.calls.push({ method: 'openPath', args: [path] })
+    await (this.stubs.get('openPath')?.(path) as Promise<void> | undefined)
+  }
+
+  /**
+   * Directory picker (recorded). The default cancels (null); stub to select.
+   * @returns the picked path, or null.
+   */
+  async pickDirectory(): Promise<string | null> {
+    this.calls.push({ method: 'pickDirectory', args: [] })
+    const stub = this.stubs.get('pickDirectory')
+    if (stub !== undefined) return await (stub() as Promise<string | null>)
+    return null
+  }
+
+  /**
+   * Rename a Workspace (recorded). The default echoes a minimal view.
+   * @param workspaceId - target workspace.
+   * @param title - new title.
+   * @returns the updated view.
+   */
+  async rename(workspaceId: WorkspaceId, title: string): Promise<WorkspaceView> {
+    this.calls.push({ method: 'rename', args: [workspaceId, title] })
+    const stub = this.stubs.get('rename')
+    if (stub !== undefined) return await (stub(workspaceId, title) as Promise<WorkspaceView>)
+    return { workspaceId, title, path: `/${title}`, sessionIds: [] } as unknown as WorkspaceView
+  }
+
+  /**
+   * Delete a Workspace (recorded; default no-op).
+   * @param workspaceId - target workspace.
+   */
+  async delete(workspaceId: WorkspaceId): Promise<void> {
+    this.calls.push({ method: 'delete', args: [workspaceId] })
+    await (this.stubs.get('delete')?.(workspaceId) as Promise<void> | undefined)
+  }
+
+  /**
+   * Move an accounted session (recorded). The default echoes a minimal view.
+   * @param workspaceId - target workspace.
+   * @param sessionId - session to move.
+   * @param beforeSessionId - anchor; omitted appends.
+   * @returns the updated view.
+   */
+  async insertSessionBefore(workspaceId: WorkspaceId, sessionId: SessionId, beforeSessionId?: SessionId): Promise<WorkspaceView> {
+    this.calls.push({ method: 'insertSessionBefore', args: [workspaceId, sessionId, beforeSessionId] })
+    const stub = this.stubs.get('insertSessionBefore')
+    if (stub !== undefined) return await (stub(workspaceId, sessionId, beforeSessionId) as Promise<WorkspaceView>)
+    return { workspaceId, title: '', path: '', sessionIds: [sessionId] } as unknown as WorkspaceView
+  }
+}