Reduce duplication across TasksApi / useTasksApi / TasksPanel handler maps

[blinkagent]

Problem

Every time a new request, command, or notification is added to the Tasks IPC layer, it must be manually defined in three places:

1. packages/shared/src/tasks/api.ts — canonical defineRequest/defineCommand/defineNotification + TasksApi object
2. packages/tasks/src/hooks/useTasksApi.ts — webview-side wrapper that re-lists every entry as a convenience method
3. src/webviews/tasks/tasksPanel.ts — extension-side requestHandlers / commandHandlers maps that re-list every entry by method name

Nothing enforces that these three stay in sync. Forgetting to wire up a new method in one of them is a silent bug — the TypeScript compiler won't catch it.

Desired outcome

• A single source of truth (TasksApi) should drive the handler/hook shape so the compiler errors when a method is missing.
• Ideally, useTasksApi and the TasksPanel handler maps could be partially or fully generated/inferred from the TasksApi definition (e.g. mapped types, helper that iterates over TasksApi entries, or codegen).
• Adding a new request/command/notification should require touching as few files as possible — ideally just the definition and the implementation.

Ideas

• Use mapped types over typeof TasksApi to derive the required handler signatures, making requestHandlers / commandHandlers type-incomplete if a handler is missing.
• Generate useTasksApi from TasksApi entries automatically (the hook is already a thin request()/command() pass-through).
• Explore a registry pattern or codegen script that reads the TasksApi object and emits boilerplate.

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Created on behalf of @EhabY