feat: Add StepTimeline support for user timeline

[pirhoo]

Summary

This PR adds support for retrieving the authenticated user's timeline (posts from followed accounts) to Trotsky, implementing the StepTimeline class with full pagination, iteration, and filtering capabilities.

Key Features

• Timeline Retrieval - Get posts from accounts the authenticated user follows
• Pagination Support - Full cursor-based pagination with .take() support
• Iteration Support - .each() for processing individual posts
• Filtering - .when() for conditional processing
• Custom Algorithms - Support for algorithm parameter (e.g., "reverse-chronological")
• Full TypeScript Types - Complete type safety with AppBskyFeedGetTimeline types

API Endpoint Used

• app.bsky.feed.getTimeline - Get authenticated user's timeline

Implementation

Core Files:

• lib/core/StepTimeline.ts - Full implementation extending StepPosts
• lib/core/Trotsky.ts - Added timeline() method
• lib/trotsky.ts - Exported StepTimeline class

Tests:

• tests/core/StepTimeline.test.ts - 12 comprehensive tests covering:
  • Cloning
  • Timeline retrieval
  • Post structure validation
  • Filtering by author
  • Pagination
  • Custom query parameters
  • Empty timeline handling
  • Algorithm parameter support

Documentation:

• docs/guide/features.md - Updated feature matrix

Usage Examples

// Get recent timeline posts
await Trotsky.init(agent)
  .timeline()
  .take(20)
  .each()
  .tap((step) => {
    console.log(`@${step.context.author.handle}: ${step.context.record.text}`)
  })
  .run()

// Like posts with specific criteria
await Trotsky.init(agent)
  .timeline()
  .take(50)
  .each()
  .when((step) => step?.context?.record?.text?.includes("#typescript"))
  .like()
  .wait(1000)
  .run()

// Use custom algorithm
await Trotsky.init(agent)
  .timeline({ algorithm: "reverse-chronological" })
  .take(10)
  .each()
  .run()

Test Results

Test Suites: 1 skipped, 31 passed, 31 of 32 total
Tests:       1 skipped, 116 passed, 117 total
Time:        302.02s

All tests passing with no regressions to existing functionality.

Files Changed

• lib/core/StepTimeline.ts - New file (116 lines)
• lib/core/Trotsky.ts - Added timeline() method
• lib/trotsky.ts - Export StepTimeline
• tests/core/StepTimeline.test.ts - New file (218 lines)
• docs/guide/features.md - Updated status

Notes

• Follows the same patterns as existing step classes (StepActorPosts, StepSearchPosts)
• Extends StepPosts for consistent post handling
• Requires authenticated user (timeline is user-specific)
• Fully compatible with all existing Trotsky features (.when(), .tap(), .take(), etc.)