copilot agent type cleanup

[roblourens]

No description provided.

[Copilot]

Pull request overview

This PR performs a small type-alignment cleanup around Copilot SDK session hooks and tool types in the agent host implementation and its tests, so local code tracks the SDK’s canonical shapes instead of maintaining hand-rolled duplicates.

Changes:

• Replace locally-defined hook/input shapes with types derived from @github/copilot-sdk (Parameters<>, ReturnType<>, Awaited<>).
• Update hook invocations in tests to match the SDK hook input shape (e.g. adding timestamp, cwd, and toolResult where required).
• Tighten tool handler typing in tests by using Tool/Pick<Tool, ...> instead of ad-hoc structural types.

Show a summary per file

File	Description
src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts	Updates test hook payloads and tool typing to match the SDK’s current hook/tool contracts.
src/vs/platform/agentHost/node/copilot/copilotPluginConverters.ts	Derives hook input types directly from SessionConfig['hooks'] and applies them to generated SDK hook handlers.
src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts	Removes local duplicated SDK request/response interfaces and derives user-input + tool-hook input types from the SDK config types.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 0