chore(ci): track Docker Hub pulls in download stats gist

[santoshkumarradha]

Summary

• update-download-stats.yml (the 6-hourly job that writes the badge gist) was capturing GitHub releases / PyPI / npm but not Docker Hub.
• As a result stats.json.sources.docker was always 0, and every analytics script that reads the gist history (e.g. marketing/analytics/gist_download_analysis.py) had no Docker series to plot.
• Docker Hub's public API only exposes a cumulative pull_count — there is no daily/historical endpoint on the free tier. The only way to reconstruct a daily Docker series is to snapshot it ourselves every few hours, which is exactly what this workflow already does for every other channel.

Change

Adds a Docker Hub fetch to the inline script:

• Hits https://hub.docker.com/v2/repositories/agentfield/control-plane/ and reads pull_count.
• Rolls the value into the total and into stats.json.sources.docker.
• Wrapped in try/catch — a Docker Hub outage falls back to docker: 0 without failing the job.

After this lands, every 6-hour gist snapshot will carry a real Docker number, and the marketing analytics will be able to chart Docker pulls over time (going forward — there is no way to recover the ~5 months of pre-existing history).

Verification

• Validated the workflow YAML parses cleanly.
• Ran the inline script body in Node 25 against a mocked github SDK and a live Docker Hub call:
  • Live pull_count returned: 11,298
  • Generated stats.json payload shape:

    {
      "total": 229874,
      "sources": { "github": 180, "pypi": 184754, "npm": 33642, "docker": 11298 },
      "lastUpdated": "..."
    }

  • Asserted: docker key present, numeric, total = sum of sources.

Test plan

• Merge and either wait for the next scheduled 6h run or trigger the workflow manually via the Actions tab.
• Confirm the new gist commit's stats.json contains sources.docker with a non-zero value.
• Confirm marketing/analytics/gist_download_analysis.py --from-gist picks up the populated docker column on the next refresh.

[santoshkumarradha]

@AbirAbbas can you validate this? Checked but not super familiar