Add Tasks panel infrastructure with type-safe IPC protocol

[EhabY]

Summary

Adds foundational infrastructure for the Tasks panel: a type-safe IPC protocol for webview-extension communication, the TasksPanel backend, and comprehensive test coverage.

Type-Safe IPC Protocol

The protocol uses phantom types (inspired by tRPC) to carry type information at compile time without runtime overhead:

// Define API with types
const getTask = defineRequest<{ taskId: string }, Task>("getTask");

// Extension: handler params and return type are inferred
requestHandler(TasksApi.getTask, (p) => this.client.getTask("me", p.taskId))

// Webview: params and response are type-checked
const task = await ipc.request(TasksApi.getTask, { taskId: "123" }); // → Task

Three message types with distinct semantics:

Type	Direction	Response	Use Case
Request	webview → extension	Yes	Data fetching, mutations
Command	webview → extension	No	Fire-and-forget actions (open URL, download)
Notification	extension → webview	No	Push updates (task changed, logs appended)

Why this design:

• Phantom types provide full type safety with zero runtime cost
• Separating requests/commands/notifications makes the communication pattern explicit
• Handler wrappers (requestHandler, commandHandler) ensure type safety at definition time, catching errors before they reach call sites
• Single TasksApi object serves as the source of truth for all messages

Package Structure

packages/
├── shared/           # Types and API definitions (used by extension + webviews)
├── webview-shared/   # React hooks (useIpc) for webview communication
└── tasks/            # Tasks panel React app

Shared types live in @repo/shared so both the extension (Node.js) and webviews (browser) import the same definitions.

TasksPanel Backend

• CRUD operations - Create, delete, pause, resume tasks
• Template management - Fetch templates and presets with 5-minute TTL cache
• Log fetching - Cached for completed/errored/paused tasks (stable states)
• Push notifications - Real-time updates via tasksUpdated notification

Closes #775

[DanielleMaywood]

Just some minor nits for now. Still haven't had time to read and digest it all