fix(mcp): pause active timeout during elicitation

[mikemikimike]

Summary

• pause the MCP tool's active-work deadline while one or more elicitation requests wait for user input
• propagate MCP request/connection cancellation to pending elicitations and preserve the existing accept/decline/cancel mapping
• keep the ordinary active-work timeout and add regression coverage for overlap, timeout, and connection-close behavior

Testing

• bun run --cwd packages/plugins/mcp test -- src/sdk/invoke.test.ts
• bun run format:check
• bun run lint
• bun run typecheck
• git diff --check

The complete MCP package suite was also exercised; its only failure was the existing Windows stdio-env-isolation HOME safe-list assertion, while the remaining 37 files passed (296 tests, 29 skipped). The repository-wide test command has a Windows Bun argument-expansion issue, and unrelated parallel filesystem/cleanup failures were recorded separately.

Fixes #1953