feat: Content performance trending over time

[saraichinwag]

Summary

Add ability to analyze content performance trends over time, not just snapshots. Agent should see if metrics are improving, declining, or stable.

The Gap

Current analytics abilities return:

• "This post has 500 pageviews"
• "This pin has 1000 impressions"

But not:

• "This post is trending UP 40% vs last month"
• "This pin's impressions have declined 20% week-over-week"
• "Traffic from Pinterest is growing, search is flat"
• "This category has negative momentum"

Use Case

Agent should be able to answer:

• "Which posts are gaining momentum?"
• "Which pins should I re-pin because they're declining?"
• "Is my Pinterest strategy working? Are impressions growing?"
• "Which categories are trending up vs down?"

Proposed Ability: datamachine/get-content-trends

Input:

• source — ga4, pinterest, bing, gsc, all
• dimension — by_post, by_category, by_traffic_source
• compare — wow (week-over-week), mom (month-over-month), yoy (year-over-year)
• period — current period length (7d, 30d, 90d)
• limit — top N to return

Output:

{
  "success": true,
  "source": "ga4",
  "comparison": "mom",
  "trending_up": [
    {
      "post_id": 12345,
      "title": "Spiritual Meaning of Crows",
      "current": 5000,
      "previous": 3000,
      "change": 2000,
      "change_pct": 66.7,
      "trend": "up"
    }
  ],
  "trending_down": [...],
  "stable": [...],
  "summary": {
    "total_change_pct": 12.5,
    "direction": "up"
  }
}

Dependencies

• Pinterest analytics (fix(ui): filter ghost steps without step_type from pipeline display #57 in data-machine-socials)
• All existing analytics abilities (GA4, Bing, GSC)

Priority

Medium — nice-to-have for strategic decisions, but raw data is sufficient for now.

Status

Future enhancement after core analytics abilities are solid.